THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

LOS  ANGELES 

GIFT  OF 


Mrs.  Clifford  B.  Walker 


TECHNIC   OF 
REFRACTION 

Trial  Case  and  Refractive  Instruments 


A  Manual  of  Practical  Refraction  with  Instruc- 
tions for  the  Operation  of  the  Trial  Case  and 
Refractive  Instruments  and  Methods 
for  Successfully  Carrying  Out 
a  Case  of  Ocular 
Refraction 


By 

THOMAS  G.  ATKINSON,  M.  D. 

Author  of  Oculo-Refractioe  Cyclopedia  and 
Dictionary,  Essentials  of  Refraction,  Func- 
tional Diagnosis,  etc.  Editor,  "The  Eye,  Ear, 
Nose  and  Throat  Monthly."  Contributor  to 
Various  Scientific  Publications  on  Oculo- 
Refraction. 


Published  by 

THE  PROFESSIONAL  PRESS,  Inc. 

Chicago,  111. 

1922 


Copyright.   1922. 


Biomedical 
Library 

ww 

-306 


FOREWORD. 

After  all  is  said  and  done,  the  practical  end  of  ocular 
refraction  consists  in  its  technique  ;  that  is  to  say,  in  the 
most  skillful  and  efficient  application  to  the  case  in  hand 
of  the  methods  and  apparatus  at  one's  disposal,  and  the 
most  intelligent  evaluation  of  their  findings.  The  proper 
manipulation  of  these  instruments  is,  therefore,  an  ex- 
ceedingly important  part  of  refraction;  it  is,  in  fact,  the 
practice  of  refraction.  The  simplest  method,  or  instru- 
ment. is  susceptible  of  all  degrees  of  value  and  efficiency, 
according  to  the  skill  and  accuracy  with  which  it  is  ap- 
plied. 

The  instructions  given  in  this  little  book  are  those  which 
the  design  of  the  various  instruments  and  the  concensus 
of  the  best  experience  have  shown  to  be  the  most  effective 
way  of  getting  all  that  is  to  be  got  out  of  the  procedure  in 
question.  Each  technique  is  set  out,  in  tabulated,  consecu- 
tive form,  step  by  step,  so  that  the  student  or  practitioner 
may,  by  its  aid,  perform  the  operation  from  start  to  finish 
without  any  uncertainty  or  hesitation.  The  book  is,  in 
short,  a  working  manual  of  practical  refraction.  If  the 
reader  has  never  yet  performed  the  task  of  refracting,  he 
may  here  learn,  at  first  hand,  precisely  how  to  proceed. 
If  he  has  been  using  the  methods  and  instruments  here 
described  by  different  technics,  he  will  find  his  work 
greatly  simplified  and  its  efficiency  increased  by  following 
the  procedures  laid  down  in  these  pages. 

THE  AUTHOR. 


CONTENTS 


CHAPTER  I 


The  Trial  Case — Stenopaic  Slit — Junes'  Method  of  Ste- 
nopaic  Slit — Chromatic  or  Cobalt  Test — Prisms — Con- 
vergence Tests — The  Maddox  Rod — Cross  Cylinder  Test 
— Visual  Acuity  Test 7 

CHAPTER  II 

The  Retinoscope — Static  Retinoscopy — Finding  the  Chief 
Meridians  —  Dynamic  Retinoscopy  —  Cross'  Method  — 
Sheard's  Method — The  Genothalmic  Retinoscope — The 
Geneva  Ophthalmoscope  —  Retinoscope  —  Thorington  Ax- 
onometer  23 

CHAPTER  III 

The  Ophthalmoscope— Direct  Method — Indirect  Method 
—The  Geneva  Ophthalmoscope  and  Retinoscope 30 

CHAPTER  IV 

The  Ophthalmometer — Universal  Ophthalmometer — C-I 
Ophthalmometer — Meyrowitz-Javal  Ophthalmometer 4'2 

CHAPTER  V 

The  Phoroptometer — The  DeZeng  Phoroptometer  or 
Phoroptcr — The  Ski-Optometer — The  Genothalmic  Re- 
fractor— Binocular  Muscle  Tests — Monocular  Muscle 
Tests — Duction  Tests — Muscle  Exercises 50 

CHAPTER  VI 

The  Perimeter — Standard  Registering  Perimeter — Stereo- 
Campimeter  with  Lloyd's  Slate 6'.) 


CHAPTER  VII 

Tests  for  Color  Blindness — Holmgren's  Wool  Test — Jen- 
ning's  Self-Recording  Test — Williams  Lantern  Test — 
Nagel's  Test 73 

CHAPTER  VIII 

Miscellaneous — The  Punctumeter — The  Ametropometer — 
The  Dynamic  Refractor — The  Placidoscope — Interpupil- 
lary  Gauge 77 

CHAPTER  IX 

The  Complete  Examination  and  Record — Vision  and 
Visual  Acuity  —  Subjective  Tests  —  Objective  Tests — 
Muscle  Tests — The  Near  Point — Correction  and  Con- 
firmation— The  Ophthalmoscope — The  Visual  Field 8."> 


CHAlTliR   1. 

THE  TRIAL  CASE. 

The  original  and  essential  contents  of  the  trial  case  con- 
sist of  sets  of  graded  ophthalmic  lenses,  plus  and  minus, 
spherical  and  cylindrical,  representing  various  dioptric 
intervals,  according  to  the  numerical  completeness  of  the 
case ;  a  set  of  prisms  graded  in  prism  degrees  or  dioptres ; 
and  a  trial  frame,  equipped  with  a  graduated  arc-rim  for 
placing  the  axis  of  a  cylinder,  in  which  to  mount  the  lenses 
and  prisms  before  the  patient's  eyes. 

The  working  value  of  these  lenses  and  prisms  depends 
upon  knowing  how  to  apply  them  to  the  detection  and 
measurement  and  correction  of  refractive  errors.  There 
are  several  systems  of  technic  for  this  working  applica- 
tion of  lenses  and  prisms. 

In  addition  to  lenses  and  prisms,  however,  every  well- 
equipped  modern  trial  case  contains  certain  other  devices 
for  the  more  rapid  and  accurate  performance  of  ocular 
refraction,  which  have  come  to  be  recognized  as  standard 
integral  parts  of  the  trial  case.  Chief  among  these  are  the 
Maddox  rod,  the  stenopaic  slit,  and  the  cobalt  or  chromatic 
glass. 

The  following  instructions  cover  the  commonly-accepted, 
standard  methods  of  employing  these  contents  of  the  trial 
case  for  testing  refraction  and  muscle  balance. 

Fogging. 

i.  With  the  chart  at  20  feet,  place  before  the  eye  to  be 
tested  [the  other  eye  being  meantime  excluded  from 


8  TECHNIC   OF   REFRACTION 

vision]   a  plus  lens  strong  enough  to  blot  out  both  test 
type  letters  and  astigmatic  wheel. 

2.  Direct  patient's   attention   to   the   astigmatic   chart. 
Gradually  reduce  the  plus  power  before  the  eye  by  put- 
ting in  front  of  it  successively  stronger  minus  spheres,— 
beginning  with  minus   .50  D.  and  increasing   .50  D  at  a 
time — until  patient  can  just  discern  the  astigmatic  wheel. 

3.  If  all  the  spokes  of  the  wheel  are  seen  with  equal 
clearness,  there  is  no  astigmatism. 

4.  If  one  of  the  spokes  stands  out  more  clearly  than  all 
the  rest,  there   is   astigmatism.     Correct  it  at  once  by 
finding  the  weakest  minus  cylinder  which,  with  its  axis 
at   right  angles  to   the   clearest   spoke,   makes   them   all 
equally  clear. 

5.  Leaving  the  cylinder  (if  any)  in  place,  continue  to 
reduce  the  plus  spherical  power  by  increasing  the  strength 
of  the  minus  sphere  -5oD.  or  even  .25  D.  at  a  time,  until 
patient  can  read  20/20  type. 

6.  The  net  amount  of  lens  power  now  before  the  eye, 
including  the  cylinder   [if  any],  is  the  patient's  distance 
correction. 

7.  If  there  is  no  astigmatism,  as  shown  by  section  3, 
then,  of  course,  item  4  will  be  omitted. 

8.  Example :  A  plus  5  D.  sphere  completely  fogs  vision. 
With  a  minus  i  D.  sphere  before  the  plus  5  D.  patient  can 
just  begin  to  see  the  astigmatic  wheel.    The  spoke  at  90 
deg.  stands  out  clearest.     A  minus  .75  cylinder,  axis  180, 
makes  all  clear  alike.     By  increasing  the  minus  sphere  to 
2  D.  patient  reads  20/20.    Correction :  minus  ,75  D.  cylin- 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS      9 

der,  axis  90,  with  a  plus  3  D.  sphere — i.e.  the  difference 
between  the  plus  5  fogging  lens  and  the  minus  2  reduc- 
ing lens. 

Stenopaic  Slit. 

1.  Place  the  slit  before  the  eye  to  be  tested,  the  other 
eye  being  meanwhile  shut  off  by  means  of  a  blank. 

2.  Slowly  revolve  the  slit  before  the  eye,  directing  the 
patient's  attention  to  the  test  chart,  until  best  possible 
vision  is  obtained,  and  note  the  angle  at  which  the  slit 
stands. 


3.  If  vision  at  this  point  is  20/20,  this  meridian  of  the 
eye  is  normal.  If  not,  try  a  weak  plus  sphere  in  front 
of  the  slit.  If  this  improves  the  vision,  find  the  plus 
sphere  which  makes  vision  20/20.  If  plus  spheres  make 
vision  worse,  change  to  minus,  and  find  the  minus  sphere 
which  makes  vision  20/20.  The  sphere,  plus  or  minus, 
which  makes  vision  20/20  is  the  measure  of  the  refractive 
error  in  this  meridian  of  the  eye. 


10  TECHNIC   OF   REFRACTION 

4.  Now  turn  the  slit  90  degrees,   to   the  meridian  of 
worst  vision,  and  repeat  the  process  described  in  section  3. 

5.  You  now  have  the  angles  of  best  and  worst  vision, 
and  the  refractive  error  [if  any]   of  each.     Prescribe  a 
cylinder  equal  to  the  difference  between  the  two  meridians, 
with  its  axis  at  right  angles  to  the  worse  meridian,  and  a 
sphere  equal  to  the  error  in  the  best  meridian. 

6.  Example  :  Vision  is  best  with  slit  at  90  deg.    A  plus 
2  sphere  makes  it  20/20.    Vision  is  worst  at  180  deg.    A 
plus  3.50  makes  it  20/20.    Correction:   A  plus  1.50  cylin- 
der, axis  90  deg.,  combined  with  a  plus  2  sphere. 

Example :  Vision  is  best  with  slit  at  30  deg.  A  plus  2 
sphere  makes  it  20/20.  Vision  is  worst  at  120  deg.  and  a 
minus  3  makes  it  20/20.  In  this  case  the  worst  meridian 
is  minus,  hence  the  correction  is:  A  minus  5  cylinder 
[algebraic  difference  between  the  two  meridians],  axis 
30  deg.,  with  a  plus  2  sphere. 

Junes'  Method  of  Using  the  Stenopaic  Slit. 

1.  Seat  the  patient  20  feet   from  a  clock  dial  chart. 
Examine  one  eye  at  a  time,  excluding  the  other  eye  from 
vision. 

2.  If,  with  the  naked  eye,  the  patient  sees  all  the  lines 
of  the  dial  equally  black,  there  is  no  astigmatism.     His 
error,  if  he  has  any,  is  spherical. 

3.  Place  the  slit  before  the  eye,  set  at  any  angle  at  ran- 
dom.    If  he  continues  to  see  all  lines  equally  black,  the 
eye  is  either  emmetropic  or  hyperopic.    Place  a  weak  plus 
sphere  before  the  slit.     If  he  now  sees  one  line  blacker 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    11 

than  the  rest  [phenomenon  of  the  black  line]  he  is  emme- 
tropic.  If  he  still  continues  to  see  all  lines  alike,  he  is 
hyperopic.  Continue  to  place  more  and  more  plus  sphere 
before  the  slit  until  the  phenomenon  of  the  black  line 
appears;  the  spherical  power  immediately  preceding  this 
is  the  measure  of  his  hyperopia. 

4.  If  on  placing  the  slit  before  the  eye  the  phenomenon 
of  the  black  line  immediately  appears,  the  eye  is  myopic. 
Place  successively  stronger  concave  lenses  before  the  slit 
until  the  phenomenon  of  the  black  line  disappears  and  all 
look  black  alike.     The  weakest  minus  lens  which  accom- 
plishes this  is  the  measure  of  his  myopia. 

5.  If,  with  the  naked  eye,  the  patient  sees  the  phenome- 
non of  the  black  line,  the  eye  is  astigmatic,  and  the  direc- 
tion of  the  clearest  line  is  one  of  the  principal  meridians. 

6.  Place  the  slit  before  the  eye  with  the  axis  of  the 
slit  coinciding  with  the  blackest  line.    If  the  phenomenon 
of  the  black  line  disappears,  the  eye  is  either  emmetropic 
or  hyperopic.     Place  a  weak  plus  sphere  before  the  slit. 
If  the  phenomenon  of  the  black  line  re-appears,  the  eye 
is  emmetropic.    If  not,  it  is  hyperopic.    Place  successively 
stronger  plus  spheres  before  the  slit  until  the  phenomenon 
re-appears.     The  spherical  power  immediately  preceding 
this  is  the  measure  of  the  hyperopia  of  that  meridian. 

7.  If,  on  placing  the  slit  before  the  eye  with  its  axis 
along  the  blackest  line,  the  phenomenon  of  the  black  line 
persists,  this  meridian  of  the  eye  is  myopic.    The  weakest 
concave  lens  which  causes  the  phenomenon  to  disappear  is 
the  measure  of  its  myopia. 


12  TECH^IC   OF   REFRACTION 

8.  Now  rotate  the  slit  to  the  opposite  angle,  at  right 
angles  to  the  first  position,  and  repeat  the  test.     In  this 
way  the  refraction  of  the  two  principal  meridians  is  ob- 
tained, and  the  correction  calculated  in  the  usual  way. 

9.  If,  with  the  naked  eye,  the  patient  cannot  distin- 
guish any  of  the  lines  on  the  dial,  the  eye  is  either  very 
myopic  or  else  there  is  hyperopia  complicated  with  astig- 
matism. 

10.  Place  a  weak  minus  lens  before  the  eye,  without 
any  slit.     If  all  the  lines  of  the  chart  become  equally  dis- 
tinct, the  eye  is  myopic  only.     Place  the  slit  before  the 
eye  at  any  angle,  and  proceed  as  in  section  4  to  measure 
to  myopia. 

11.  If,  with  the  concave  lens,  the  phenomenon  of  the 
black  line  appears,  there  is  compound  myopic  astigma- 
tism.   Place  the  slit  before  the  eye,  with  its  axis  coincid- 
ing with  the  blackest  line,  and  proceed  to  measure  the 
two  principal  meridians  as  instructed  in  Sections  7  and  8. 

12.  If  a  concave  lens  does  not  improve  the  vision,  place 
before  the  naked  eye  a  convex  lens  sufficiently  strong  to 
give  vision  of  the  dial.     If  all  the  lines  of  the  chart  now 
become  equally  clear,  the  eye  is  highly  hyperopic  only. 
Place  the  slit  before  the  eye  at  any  angle,  and  proceed  as 
instructed  in  Section  3  to  measure  his  hyperopia. 

13.  If,  with  the  convex  lens,  the  phenomenon  of  the 
black  line  appears,  there  is  compound  hyperopic  astig- 
matism.    Place  the  slit  before  the  eye,  with  its  axis  coin- 
ciding with  the  blackest  line,  and  proceed  to  measure  the 
two  principal  meridians  as  instructed  in  Sections  6  and  8. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS     13 

14.  If,  in  the  carrying  out  of  the  tests  in  any  of  the 
cases  of  astigmatism,  one  meridian  exhibits  the  signs  of 
hyperopia  and  the  other  of  myopia,  the  astigmatism  is,  of 
course,  mixed.  Each  meridian  is  to  be  measured  accord- 
ing to  its  kind  of  error. 

Chromatic  or  Cobalt  Test. 

1.  With  the  cobalt  lens  before  the  eye  to  be  tested,  [the 
other  eye  being  excluded  from  vision],  the  patient's  at- 
tention is  directed  to  a  small  circular  light,  usually  at  20 
feet. 

2.  If  patient  is  hyperopic,  he  sees  a  violet  centre  with 
a  ring  of  red  around  it.     Plus  correction  is  added  until 
he  sees  no  more  red  around  the  centre,  or  until  there  is 
a  slight  blue  ring. 


3.  If  patient  is  myopic,  he  sees  a  red  center  with  a  blue 
ring  around  it.     Minus  spherical  correction  is  added  until 
he  sees  no  blue  ring,  or  until  it  is  very  faint. 

4.  If  patient  has  hyperopic  astigmatism,  he  sees  red  on 
each  side  of  the  blue,  corresponding  to  the  chief  meridians 


14  TECHNIC    OF   REFRACTION 

of  the  astigmatism.  Add  plus  correction  until  the  red  on 
each  side  almost  disappears,  then  minus  cylinders,  axis 
where  the  red  shows,  until  the  red  appears  at  right  angles 
to  the  axis  of  the  cylinder,  i.e.  until  a  red  ring  appears 
around  the  center.  Now  add  plus  spherical  power  until 
there  is  no  longer  a  red  ring,  but  a  thin  blue  ring. 

5.  If  patient  has  myopic  astigmatism,  he  sees  blue  on 
each  side  corresponding  to  the  chief  meridians.     Put  on 
minus  cylinders  until  there  is  a  red  ring  around  the  center ; 
then  add  plus  spherical  lenses  until  there  is  no  red  ring, 
but  a  narrow  blue  ring. 

6.  If  patient  has  mixed  astigmatism,  he  sees  blue  up 
and  down  and  red  on  each  side,  or  vice  versa.     Put  on 
plus  spheres  until  there  is  a  little  red  left  in  its  place; 
then  minus  cylinders,  axis  where  the  red  is,  until  there  is 
a  red  ring  around  the  center.     After  that,  add  plus  spher- 
ical power  until  there  .is  no  more  red  ring,  but  a  thin  blue 
ring. 

Prisms. 

Prisms  are  used  for  three  distinct  purposes  :  [  i  ]  To  test 
the  functional  strength  or  efficiency  of  the  extrinsic  mus- 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS     15 

cles,  [2]  To  exercise  defective  muscles,  [3]  To  test  con- 
vergence. 

Duction. 

1.  Seat  the  patient  20  feet  from  a  small  white  circle  of 
light,  with  his  eyes  on  the  same  horizontal  plane  with  the 
light.     Instruct  him  to  look  steadily  at  the  light. 

2.  To  test  the  duction  of  the  internal  recti  muscles,  be- 
gin with  a  small  strength  prism,  base  in,  and  gradually 
add  more  and  more  prism  power,'  base  in,  until  the  patient 
can  no  longer  maintain  single  vision  of  the  light. 

N.  B. — It  is  advisable  to  add  this  prism  power  equally 
to  both  eyes,  as  far  as  possible,  and  to  proceed  by  as  small 
stages  of  increase  as  practicable. 

A  normal  pair  of  eyes  should  be  able  to  overcome  about 
30  prism  dioptres,  divided  between  the  two  eyes. 

3.  To  test  the  duction  of  the  externals,  proceed  in  the 
same  fashion,  but  with  the  prisms  placed  base  out.     A 
normal  pair  of  eyes  should  overcome  about  8  to  10  prism 
dioptres. 

4.  To  test  the  vertical  muscles,  the  same  procedure  is 
called  for,  with  the  base  of  the  prism  down  to  test  the 
superior  recti,  base  up  to  test  the  inferior.     Normal  ver- 
tical muscles  should  overcome  4  to  6  prism  dioptres. 

Muscle  Exercises. 

To  exercise  the  ocular  muscles,  the  same  procedure  is 
required  as  in  testing  their  duction,  but  the  exercises  must 
be  cautiously  graded,  increasing  the  power  of  the  prisms 
gradually,  over  several  sittings,  until  the  patient  is  able 


16  TECHNIC    OF    REFRACTION 

to  overcome  his  normal  amount.  Put,  always,  the  apex 
of  the  prism  over  the  muscle  to  be  exercised,  and  divide 
the  prism  power  between  the  two  eyes,  unless,  of  course, 
it  is  desired  to  exercise  one  eye  specially. 

N.  B. — Rotary  prisms  are  much  preferable  for  duction 
and  muscle  exercises,  as  they  permit  of  continuously 
graded  increase  of  prism  power. 

Convergence  Tests. 

There  are  numerous  varieties  of  this  test,  differing 
principally  in  the  nature  of  the  chart  employed,  such  as 
the  dot  and  line,  the  line  of  type  recommended  by  Sheard, 
and  others.  They  are  all  essentially  the  same,  however, 
in  principle  and  general  technique,  and  we  shall  here  de- 
scribe the  test  in  connection  with  the  graded  line  and 
index  pointer.  The  chart  consists  of  a  horizontal  black 
line,  from  the  middle  of  which  rises  a  black  index  pointer, 
about  a  centimeter  in  height.  On  either  side  of  the 
pointer  the  line  is  graded  into  centimeters. 

1.  With  the  chart  held  25  cm.  from  the  patient's  eyes 
[or  at  whatever  distance  the  test  is  to  be  made]  place  be- 
fore one  eye  a  6  dioptre  prism,  base  up.     This  will  make 
the  black  line  appear  double,  the  false  line,  seen  by  the 
prismed  eye,  being  below  the  true  one. 

2.  If  the  index  pointer  of  the  lower  line  stands  ex- 
actly under  the  pointer  of  the  upper  line,  there  is  no  im- 
balance. 

3.  If  the  index  pointer  stands  to  one  side  of  the  pointer 
of  the  upper  line,  toward  the  same  side  as  the  prismed 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS     17 

eye,  there  is  esophoria.  Note  the  number  of  centimeters 
on  the  upper  line  scale  to  which  the  lower  pointer  points. 
Divide  this  number  by  the  distance  in  meters  at  which  the 
test  is  made,  to  find  the  prism  dioptres  of  esophoria. 

Thus,  if  the  lower  pointer  is  shifted  so  as  to  stand  at 
i  cm.,  then  i  divided  by  .25  equals  4  prism  dioptres  of 
esophoria. 

4.  If  the  lower  index  pointer  is  shifted  to  the  opposite 
side  from  that  of  the  prismed  eye,  there  is  exophoria,  to 
be  measured  in  the  same  way  as  the  esophoria  in  the  pre- 
vious paragraph. 

N.  B. — It  is  best  to  make  a  practice  of  always  plac- 
ing the  displacing  prism  before  the  same  eye — say  the 
right  eye — so  that  esophoria  will  always  be  shown  by 
the  lower  pointer  shifting  to  the  right,  and  exophoria  by 
its  shifting  to  the  left. 

5.  To  test  the  vertical  muscles,  turn  the  chart  so  that 
the  black  line  is  vertical,  and  place  before  the  right  eye  a 
12  or  15  dioptre  prism,  base  in,  which  will  double  the  line 
laterally. 

6.  If  the  two  index  pointers  are  level  with  each  other, 
there  is  no  imbalance.     If  the  pointer  of  the  false  line  is 
shifted  up  or  down,  vertical  imbalance  is  indicated,  hyper- 
phoria  of  right  or  left  eye,  as  the  case  may  be,  and  the 
amount  is  found,  as  before,  by  dividing  the  distance  [in 
meters]    into  the  centimeter   scale  at   which   the  shifted 
pointer  stands. 


18  TECHNIC   OF  REFRACTION 

The  Maddox  Rod. 

The  purpose  of  this  is  to  dissociate  the  retinal  images, 
so  that  the  extrinsic  muscles  of  the  eyes  will  assume  their 
position  of  rest,  and  thus  disclose  any  imbalance  which 
may  exist.  Its  use  is  limited  to  tests  at  infinity. 

1.  Seat  the  patient  twenty  feet  from  the  object,  which 
should  be  a  small  circle  of  white  light. 

2.  For  testing  the  lateral  muscles,  place  the  Maddox 
rod  before  one  eye  and  either  leave  the  other  uncovered 


or  place  before  it  a  plane  red  glass — the  latter  is  better,  so 
as  to  make  the  images  further  dissimilar.  Turn  the  rod 
with  its  axis  at  180  degrees ;  this  will  draw  out  the  light 
into  a  vertical  streak,  while  the  other  eye  sees  a  red  circle 
of  light. 

3.  If  the  two  images — the  white  streak  and  the  red  cir- 
cle of  light — are  separated  in  the  same  direction  as  the 
eyes  viewing  them,  there  is  esophoria.  The  weakest 
prism,  with  its  base  out,  which  will  bring  the  two  images 
together,  is  the  measure  of  the  esophoria. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS     1!) 

4.  If  the  two  images  are  separated  in  the  opposite  di- 
rection from  the  eyes  viewing  them — i.e.,  with  the  rod  be- 
fore the  right  eye,  the  white  streak  is  seen  to  the  left 
side — ["crossed"] — there     is    exophoria.     The     weakest 
prism,  with  its  base  in,  which  brings  the  images  together 
is  the  measure  of  the  exophoria. 

5.  For  testing  the  vertical  muscles,  set  the  rod  at  90 
deg.,  which  presents  a  horizontal  streak  of  white  light. 

6.  If  the  two  images  are  separated,  one  above  the  other, 
there  is  vertical  imbalance.     The  weakest  prism,  placed 
base  up  before  the  eye  whose  image  is  underneath,  or  base 
clown  before  the  eye  whose  image  is  above,  which  brings 
the  two  images  together  on  the  same  horizontal  plane,  is 
the  measure  of  the  error. 

7.  Place  two  Maddox  rods,  one  before  each  eye,  both 
set  either  at  90  or  at  180  degrees.     If  the  white  streak 
does  not  appear  to  the  patient  to  be  horizontal  or  vertical, 
respectively,  but  oblique,  there  is  cyclophoria,  which  may 
be  measured  by  turning  the  rod  in  the  trial-frame  until  the 
streak  appears  vertical  or  horizontal,  as  the  case  may  be. 
The  number  of  degrees  that  the  rod  then  stands  from  90 
or  180  is  the  measure  of  the  cyclophoria. 

Cross-Cylinder  Test. 

i.  Having  determined  the  patient's  near  point  by  the 
ordinary  methods,  and  [in  the  case  of  presbyopia]  prop- 
erly corrected,  substitute  for  the  type  chart  a  T  chart, 
and  place  before  the  eye  a  compound  lens  equivalent  to  a 
cross-cylinder,  say  a  plus  .50  sphere  and  a  minus  I  cylin- 
der, axis  90,  thus  creating  a  false  astigmatism  of  .50  D, 


20  TECHNIC    OF   REFRACTION 

hyperopic  in  one  meridian  and  .50  D.  myopic  in  the  other. 
2.  If,  before  applying  this  test,  the  eyes  were  in  exact 
focus  for  near  point,  there  will  be  no  perceptible  differ- 
ence in  the  two  arms  of  the  T. 


3.  If  one  arm  of  the  T  is  blacker  than  the  other,  then 
the  eyes  were  not  in  exact  focus.  Add  plus  spherical 
power  until  the  two  arms  are  equally  black.  This  repre- 
sents the  patient's  true  correction  for  near  point. 

Ives  Screen. 

1.  Turn  the  gratings  so  that  the  bands  or  squares  are 
too  small  to  be  visible  to  the  patient. 

2.  Rotate  the  gratings  very  slowly  by  means  of  the 
milled  head  until  patient  is  just  able  to  discern  the  pat- 
tern.    Read  the  acuity  direct  from  the  scale. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    21 

3.  Ask  the  patient  in  what  direction  the  lines  lie. 
Change  this  direction  between  tests  so  that  patient  will  not 
know  which  way  to  expect  them  to  appear. 


4.  For  subjective  test  reduce  the  lines  or  squares  from 
easy  visibility  to  just  visibility ;  for  objective  test,  increase 
them  from  non-visibility  to  just  visibility.     In  the  first  in- 
stance, accommodation  is  an  active   factor,  in  the  latter 
the  accommodation  is  at  rest. 

5.  To  locate  the  axis  of  astigmatism,  use  the  lines.    Set 
the  gratings  so  that  the  lines  are  barely  visible. 

6.  Rotate  until  the  lines  are  orientated  together  in  their 
holder  so  that  the  bands  appear  clearest.     Read  the  angle 
from  the  degree  scale  on  back  of  front  plate. 

/.  To  verify  the  result,  reduce  still  more  the  width  of 
the  lines,  and  when  the  minimum  width  of  line  visible 


22  TECHNIC    OF    REFRACTION 

to  the  patient  is  reached,  orient  the  entire  screen  to  right 
or  left,  and  the  lines  will  disappear. 

8.  When  using  the  squares,  the  brightness  of  the  light 
remains  constant.  But  when  using  the  lines,  move  the 
lamp  toward  or  away  from  the  gratings,  by  means  of  the 
sliding  sleeve,  so  as  to  vary  the  intensity  of  illumination 
in  a  manner  to  keep  the  field  uniformly  illuminated. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    23 

CHAPTER  II. 

THE  RETINOSCOPE. 

The  retinoscope  furnishes  the  only  available  objective 
method  of  determining  the  refraction  of  the  eye,  by  means 
of  shadow  phenomena  produced,  observed,  and  modified 
by  means  of  the  instrument. 

Considerable  practice  is  needed  to  be  able  to  execute 
the  manoeuvers  necessary  to  obtain  a  good  "reflex,"  and 
to  observe  the  shadows;  and  not  until  this  has  become 
easy  can  the  operator  devote  the  requisite  attention  to 
interpreting  the  shadows.  To  attain  this  proficiency  it  is 
advisable  to  practice  with  a  schematic  eye. 

It  is  assumed  in  the^e  instructions  that  the  operator  is 
familiar  with  this  elementary  phase  of  retinoscopy. 

In  the  technique  here  described  it  is  further  assumed 
that  the  operator  is  using  a  plane  mirror.  Some  retino- 


scopes  are  made  with  a  concave  mirror,  the  advantages 
of  which  are  a  more  intense  light  and  the  usefulness  of 
such  a  mirror  for  ophthalmoscopy.  If  a  concave  mirror 


24  TECH  NIC   OF    REFRACTION 

is  used,  two  points  must  be  observed  :  [  i  ]  The  operator 
must  take  care  that  he  works  at  such  a  distance  from  the 
patient  as  to  be  outside  the  focal  length  of  the  mirror; 
[2]  The  movements  of  the  shadow  will  be  precisely  the 
opposite  of  those  seen  with  the  plane  mirror. 

Many  beginners  with  the  retinoscope  make  the  mistake 
of  watching  the  disc  of  light  [made  by  the  mirror]  as  it 
passes  to  and  fro  across  the  patient's  face,  instead  of 
watching  the  shadows  in  the  pupil,  thus  failing  to  get 
proper  results.  The  light  will,  of  course,  always  move  in 
the  same  direction  that  the  mirror  is  being  moved,  and 
has  nothing  to  do  with  the  case.  It  is  the  shadows  that 
must  be  observed. 

There  are  two  methods  in  retinoscopy,  the  static  and 
dynamic.  The  former  is  employed  with  the  patient's  ac- 
commodation at  rest;  the  latter  with  the  accommodation 
in  force.  So  far  as  the  technical  aspects  of  these  two 
methods  is  concerned,  the  difference  lies  in  the  fact  that 
in  static  retinoscopy  we  employ  a  neutralizing  or  "work- 
ing equivalent"  lens,  to  equalize  the  distance  at  which  we 
work,  while  in  the  dynamic  method  no  equalizing  or  work- 
ing lens  is  used. 

Static  Retinoscopy. 

i.  The  examination  should  be  made  in  a  darkened 
room — not  necessarily  pitch  dark,  but  sufficiently  dark- 
ened that  the  patient's  pupil  when  illuminated  by  the 
mirror  shall  stand  out  conspicuously  in  contrast  to  the 
surrounding  darkness,  on  the  same  principle  that  the  body 
of  a  theater  is  darkened  to  show  up  the  illuminated  stage. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    25 

2..  If  a  non-illuminating  retinoscope  is  used,  the  source 
of  light  should  be  placed  just  back  of  the  patient's  head, 
slightly  to  one  side,  on  a  level  with  the  top  of  the  ear. 
The  best  form  of  light  is  an  incandescent  electric  lamp,  of 
50  candle  power,  enclosed  in  an  opaque  chimney,  with  an 
adjustable  diaphragm  through  which  the  light  may  emerge. 
At  the  outset  of  the  examination  the  diaphragm  should 
be  about  10  mm.  in  diameter;  as  neutralization  is  ap- 
proached, it  should  be  reduced  to  half  that  diameter. 

3.  Seat  the  patient  comfortably  in  a  chair,  either  with 
his  head  against  a  head-rest  or  leaning  slightly  forward, 
and  instruct  him  to  look  straight  in  front  of  him  into  in- 
finity.   For  this  purpose  it  is  better  not  to  have  the  room 
perfectly  dark,  or  the  patient  will  be  tempted  to  fix  his 
eyes  on  the  mirror  of  the  retinoscope.     If  the  room  be 
merely  darkened,  he  can  fix  upon  some  object  at  20  feet, 
e.g.,  the  distance  test  chart.    For  children  a  moving  object 
[e.g.,  a  revolving  wheel]  at  20  feet  distance  is  an  excel- 
lent "fixer." 

4.  Adjust  your  own  stool  so  that  your  eyes  are  on  the 
same  horizontal  plane  with  those  of  the  patient.     The  dis- 
tance from  the  patient  at  which  you  work  is  immaterial, 
except  for  purposes  of  convenience  and  clear  vision  of 
the  shadows.    Fifty  centimeters  is  a  very  convenient  work- 
ing distance.     The  important  point  is  to   determine  the 
distance  accurately.    This  is  perhaps  best  done  by  means 
of  a  tape  measure  attached  to  a  movable  bar  or  stand 
which  can  be  placed  in  a  vertical  plane  with  the  patient's 
forehead. 

5.  Place  in  the  trial   frame  before  the  patient's  eye  a 


20  TECHNIC    OF    REFRACTION 

plus  lens  whose  focal  length  is  equal  to  the  distance  at 
which  you  are  working.  This  lens,  known  as  the  "work- 
ing equivalent"  or  "equalizing  lens,"  is  to  be  regarded  as 
part  of  the  patient's  eye,  and  not  to  figure  in  any  of  the 
calculations  of  his  error. 

6.  Throwing  the  light  from  the  mirror  into  the  patient's 
pupil,  as  nearly  as  possible  along  the  visual  axis,  rotate  it 
slightly,  and  not  too  fast,  in  the  horizontal  meridian.    Too 
wide  and  too  rapid  excursions  of  the  mirror  defeat  one's 
purpose,  making  it  impossible  to  observe  the  shadows. 

7.  If  no  shadows  are  seen  to  move  across  the  patient's 
pupils,  the  refraction  is  normal  in  that  meridian. 

8.  If  a  shadow  is  seen  to  move  across  the  pupil,  one 
from  each  side,  in  the  same  direction  that  the  mirror  is 
being  rotated,  ["with  the  mirror"],  the  eye  is  hyperopic 
in  that  meridian.     If  the  edges  of  the  shadows  are  cres- 
centic  and  vertical,  the  error  is  probably  a  spherical  one ; 
if  the  edges  are  straight  and  vertical,  it  is  probably  an 
astigmatism  with  its  chief  meridians  "right,"  i.e.,  vertical 
and  horizontal.     In  either  case,  proceed  to  correct  that 
meridian.     If,  however,  the  edges  of  the  shadows  are  in- 
clined or  tipped,  then  change  the  movement  of  the  mirror 
so  as  to  rotate  it  at  right  angles  to  the  edges  of  the  shad- 
ows. 

9.  With  the  shadows  moving  "with  the  mirror,"  put  a 
plus  lens  in  the  trial  frame  before  the  eye,  beginning  with 
low  power,  and  add  to  it  until  no  shadows  can  be  seen 
moving  across  the  pupil.     The  "point  of  reversal"  has 
now  been  reached,  and  the  shadows  "neutralized."     To 
make  sure,  add  a  little  more  plus  lens,  and  observe  that 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    27 

the  movement  of  the  shadows  changes  to  the  opposite  di- 
rection. The  lens  power  which  just  succeeded  in  abolish- 
ing the  shadows  is  the  measure  and  the  correction  of  the 
error  in  this  meridian. 

N.  B. — Two  other  indications  are  to  be  watched  for  at 
this  point.  First,  when  the  point  of  neutralization  is 
reached  the  appearance  of  the  pupillary  reflex  will  change 
from  a  dull  red  to  a  bright  orange.  Second,  if  the  eye 
is  astigmatic,  as  the  point  of  reversal  is  approached  a  band 
or  streamer  of  light  will  be  seen  lying  across  the  corrected 
meridian,  due  to  the  fact  that  one  meridian  is  corrected 
while  the  opposite  one  is  still  out  of  focus. 

10.  If,  upon  first  beginning  to  rotate  tne  mirror,  shad- 
ows are  seen  moving  across  the  pupil  in  the  opposite  direc- 
tion to  that  in  which  the  mirror  is  being  rotated,  the  eve 
is  myopic  in  that  meridian  and  minus  lens  power  must  be 
used  to  neutralize  them.     All  the  other  stipulations  of  sec- 
tions 8  and  9  apply  equally  to  such  a  case. 

11.  Having  satisfactorily  neutralized  the  meridian  un- 
der examination,  make  a  notation  of  the  angle  of  the 
meridian  and  the  kind  and  amount  of  lens  power  needed 
to  neutralize  it. 

12.  With  the  correction   left  in  the  trial   frame,  now 
rotate  the  mirror  in  a  direction  exactly  at  right  angles  to 
its  former  rotation,  thus  "shadowing"'  the  opposite  chief 
meridian.     If  no  shadows  are  seen  to  move  across  the 
pupil  in  this  direction,  this  meridian  is  also  corrected,  and 
the  error  is  a  spherical  one — simple  hyperopia  or  myopia, 
as  the  case  may  be. 


28  TECHNIC    OF   REFRACTION 

13.  If  shadows  are  seen  moving  in  this  meridian  "with 
the  mirror,"  this  meridian  is  still  hyperopic.     The  case  is 
one  of  astigmatism.     Place  a  weak  plus  cylinder  in  the 
trial  frame,  with  its  axis  at  the  opposite  meridian  to  the 
one  you  are  shadowing,  and  increase  this  cylinder  until  the 
shadow  in  this  meridian  is  abolished.     The  power  of  this 
cylinder,  added  to  the  power  of  the  sphere  already  before 
the  eye,  is  the  measure  of  the  error  in  this  meridian.     The 
sphere  and  the  cylinder,  as  they  stand  in  the  trial  frame,  is 
the  correction  of  the  total  error. 

14.  If,  on  beginning  to  shadow  the  second  meridian, 
shadows  are  seen  moving  "against  the  mirror,"  this  merid- 
ian is  still  myopic,  and  minus  cylinder  lens  power  must 
be  used  to  neutralize  it,  in  the  way  described  in  section 
13.     The  net  sum  of  this  cylinder  and  the  sphere  already 
before  the  eye,   excluding  the   neutralizing  or   working 
lens,  is  the  measure  of  the  error  in  this  meridian,  and 
the  sphere  and  cylinder,  as  they  now  stand  in  the  trial 
frame,  constitute  the  total  correction. 

15.  If,  on  first  beginning  to  shadow  the  eye,  the  shad- 
ows are  seen  to  move  inconsistently,  with  the  mirror  in 
some  meridians  and  against  it  in  others,  and  the  pupillary 
area  a  mixture  of  light  and  shadow,  there  is  probably  an 
irregular  astigmatism.     In  such  a  case  find  the  best  posi- 
tion of  observation,  and  pick   out  the  meridians   which 
present  the  clearest  shadows. 

16.  If  the  shadows,  instead  of  moving  regularly  from 
side  to  side  of  the  eye,  with  or  against  the  mirror,  seem 
to  divide  into  two,  which  move  toward  each  other,  ["scis- 
sors movement"],  it  signifies  one  of  three  things,  [i]  ir- 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    29 

regular  astigmatism,  [2]  tilted  crystalline  lens,  or  [3] 
lack  of  alignment  of  the  refracting  media  of  the  eye. 
In  such  cases  be  sure  to  refract  along  the  line  of  vision ; 
watch  carefully  for  the  division  line,  and  refract  that  por- 
tion of  the  eye  in  which  the  reflex  contains  the  visual  line. 

Finding  the  Chief  Meridians. 

In  some  cases  the  two  chief  meridians  of  the  astig- 
matic eye  reveal  themselves  under  retinoscopy  by  the 
straight  edges  of  the  shadows  and  the  angle  at  which 
these  edges  lie,  as  described  in  Section  8.  In  other  cases 
these  indications  are  not  clear,  and  the  operator  must  go 
on  shadowing  the  horizontal  meridian  until,  as  neutraliza- 
tion is  approached,  the  astigmatic  band  appears  and  indi- 
cates the  lay  of  the  chief  meridians. 

To  render  this  band  as  clear  as  possible,  as  soon  as  the 
meridian  you  are  shadowing  becomes  neutralized,  push 
the  lamp  away  from  your  mirror,  or  draw  it  toward  it, 
until  the  astigmatic  band  stands  out  distinctly,  and  the 
axis  of  the  astigmatism  will  be  revealed.  This  manoeuvre 
is,  of  course,  not  practicable  with  a  self -illuminating 
retinoscope. 

Dynamic  Retinoscopy. 

Use  the  same  kind  of  retinoscope  as  for  the  static  test, 
except  that  it  should  have  a  row  of  letters  attached  to 
the  top  of  the  mirror  for  the  patient  to  fix  with  his  vision. 
The  position  of  the  patient  and  operator  are  the  same  as 
in  static  retinoscopy.  No  neutralizing  or  working  lens  is 


30  TECHNIC    OF    REFRACTION 

used  in  this  test.  As  this  is  a  binocular  test,  in  which 
convergence  is  to  play  a  part,  both  eyes  should  be  left 
uncovered. 

Cross'  Method. 

• 

1.  Seating  yourself  at  any  convenient  distance — say  50 

cm. — from  the  patient,  instruct  him  to  read  aloud  the  let- 
ters on  the  top  of  the  mirror.  According  to  Cross,  he 
will  exercise  only  that  amount  of  accommodation  which 
corresponds  to  the  3 — I  ratio  between  convergence  and 
accommodation. 

2.  Rotating  the  mirror,  as  in  the  static  technique,   if 
there  is  no  shadow,  the  refraction  of  the  eye  is  normal, 
convergence  and  accommodation  being  in  mathematical 
harmony,  and  the  retina  being  conjugate  with  the  mirror. 

3.  If  the  shadow  is  seen  to  move  with  the  mirror,  pa- 
tient is  hyperopic.     Add  plus  lens  power  before  the  eye 
until  the  shadow  is  abolished.     If  this  neutralizing  lens 
power  is  the  same,  or  substantially  the  same,  as  arrived 
at  by  the  static  test,  it  represents  the  measure  and  cor- 
rection of  the  total  error.     If  it  is  noticeably  more  than 
in  the  static  test,  the  difference  between  them  represents 
latent  hyperopia,  in  the  form  of  ciliary  spasm. 

4.  If  the  shadow  is  seen  to  move  against  the  mirror, 
patient  is  myopic.     Ordinarily  in  such  cases  the  test  may 
be  abandoned,  since  dynamic  skiascopy,  by  Cross'  method, 
has  no  special  value  in  myopia.     If  you  decide  to  continue 
it,  however,  put  on  a  strong  enough  minus  lens  to  make 
the  shadow  move  with  the  mirror,  and  then  proceed  as 
though  the  eye  were  hyperopic,  taking  care  to  subtract 
the  amount  of  the  minus  lens  from  the  final  result. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    .'51 

5.  If  latent  hyperopia,  or  ciliary  spasm,  is  shown  to 
be  present,  correct  all  or  as  much  of  it  as  your  judgment 
dictates,  in  addition  to  the  manifest  error,  as  shown  by  the 
static  test. 

6.  In  carrying  out  this  method,  the  same  indications  of 
astigmatism   must   be  watched    for,  and  the  same  steps 
taken  to  determine  and  correct  the  two  chief  meridians, 
as  set  forth  in  describing  the  static  test  [see  above] . 

Sheard's  Method, 

According  to  Sheard,  the  only  real  value  of  dynamic 
skiascopy  is  to  determine  the  patient's  true  near  point, 
i.e.,  the  near  point  where  convergence  and  accommoda- 
tion coincide.  For  this  purpose  he  has  formulated  the 
following  method  of  procedure : 

1.  First  determine  the  patient's  distance  error,  and  let 
him  wear  his  distance  correction  during  the  dynamic  test. 

2.  Push  the  fixation  chart  in  advance  of  the  retinoscope, 
say  two  or  three  inches,  and  while  he  reads  the  letters 
shadow  the  eye. 

3.  If  the  movement  of  the  shadow  is  with  the  mirror, 
push  the  chart  further  forward  until  the  movement  be- 
comes against,  and  come  forward  with  the  mirror  until  it 
changes  again  to  "with." 

4.  Repeat  this  manoeuvre  until,  with  the  chart  some  dis- 
tance in  front  of  the  mirror,  you  locate  the  nearest  point 
of  neutralization.     This  point  is  the  patient's  true  near 
point,  upon  which  his  reading  correction  is  to  be  calcu- 
lated. 


32  TECHNIC    OF   REFRACTION 

The  Genothalmic  Retinoscope. 

This  is  a  special  form  of  self -illuminating  retinoscope 
for  performing  retinoscopy. 

1.  First  unscrew  the  upper  part  of  the  head  from  the 
lower  part  and  see  that  the  lamp  is  securely  screwed  into 
place.     Then  reassemble  the  base  and  the  head,  and  se- 
curely lock  them  together. 

2.  Place  the  head   on  the  battery  handle,  hitting  the 
dent  in  the  base  of  the  head  into  the  milled  slot  in  the 
battery  handle  stem,  and  lock  by  turning  a  quarter  of  a 
turn  to  right  or  left. 

3.  Turn  on  the  current  by  revolving  to  the  right  the 
nickeled  ring  No.  2  on  the  head  of  the  battery  handle. 

4.  Hold  the  mirror  40  inches  from  a  screen,  and  move 
the  ferrule  tube  on  the  stem  up  or  down,  until  the  area 
of  light  is  nearest  to  a  circular  form  and  about  the  size  of 
a  dollar.     This  is  the  average  place  to  use  the  light,  but 
if  more  intensity  is  required,  it  may  be  obtained  by  mak- 
ing the  light-area  smaller. 

5.  Now  apply  the  instrument  to  your  face  so  that  it 
rests  securely  against  the  nose  and  eyebrow  with  the  sight- 
hole  directly  in  front  of  your  pupil,  but  with  the  mirror 
side  away  from  the  eye,  and  proceed  to  use  it. 

The  Geneva  Ophthalmoscope  and  Retinoscope. 

To  use  the  instrument  as  a  Retinoscope : 

i.  Turn  the  ophthalmoscope  lens  down  against  the  bot- 
tom of  the  tube,  and  see  that  zero  appears  on  dials  Nos. 
18  and  22,  and  the  letters  RET  on  dial  No.  16. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    33 

2.  Seat  patient  facing  away  from  window  or  strong 
light,  and  place  instrument  so  that  patient  can  see,  with 
either  eye,  a  test  chart  placed  preferably  20  feet  away. 
Any  ordinary  test  chart  will  do.     It  steadies  the  patient's 
fixation  and  relaxes  his  accommodation. 

3.  Have  patient  place  his  chin  in  the  chin-rest  and  his 
forehead  in  head-rest,  with  face  squarely  fitted  to  the 
frame.    Direct  him  to  look  at  the  test-chart. 


4.  Run  the  instrument  up  toward  patient  as  far  as  it 
will  go,  using  handles  No.  9  for  that  purpose.     Place  in 
lens  clip  No.  25  a  plus  lens  of.  such  power  as  to  fog  pa- 
tient's vision  to  about  the  80  line  on  chart ;  ask  him  to  read 
as  many  letters  as  he  can  on  this  and  the  following  line. 
This  relaxes  accommodation  very  thoroughly. 

5.  See  that  the  center  of  the  end  of  the  tube  is  in  line 
with  center  of  patient's  pupil. 

6.  Look  through  peep-hole,  and  the  reflex   from  pa- 
tient's pupil  will  be  seen  at  other  end  of  tube,  as  a  round, 
red-illuminated  area. 

7.  If  reflex,  instead  of  being  orange-red,  is  a  silvery 
white,  the  patient  is  looking  at  too  great  an  angle  from  the 
line  of  the  instrument,  and  the  chart  must  be  moved  so 


34  TECHNIC   OF   REFRACTION 

that  the  line  of  vision  will  be  closer  to  the  axis  of  the  in- 
strument. If  the  reflex  is  a  dirty  grayish- white,  patient  is 
accommodating,  and  more  fogging  [plus]  lens  must  be 
used. 

8.  When  the  proper  color  of  reflex  is  obtained  [orange 
red]  tilt  the  mirror  back  and  forth  slowly,  by  means  of 
handle  No.  35,  and  note  the  movements  of  the  shadow 
in  the  patient's  pupil. 

9.  The  mechanism  permits  of  the  mirror  being  tilted 
to  and  fro  across  any  meridian  of  the  eye.     Use  the  mir- 
ror precisely  as  you  would  the  hand  retinoscope,    [see 
Instructions  for  Static  Retinoscopy],  rotating  into  place 
any  desired  correcting  lens,  or  combination  of  lenses,  by 
means  of  dial  wheels  Nos.  16  and  18. 

Thorington  Axonometer. 

A  device  to  aid  in  finding  the  exact  axis  subtended  by 
the  band  of  light  in  retinoscopy. 


i.  Place  the  disc  in  the  trial  frame  so  that  the  cornea 
of  the  examined  eye  coincides  with  the  central  opening 
in  the  disc. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    35 

2.  When  the  first  meridian  of  astigmatism  has  been 
found  and  corrected,  so  that  the  astigmatic  band  appears, 
slowly  turn  the  axonometer  until  the  two  heavy  white 
lines  appear  to  make  a  continuous  line  with  the  band  of 
light. 

3.  The  degree  on  the  scale  to  which  the  arrow  points 
is  the  axis  for  the  correcting  cylinder. 


80  TECHNIC   OF   REFRACTION 

CHAPTER  III. 

THE  OPHTHALMOSCOPE. 

The  ophthalmoscope  is  not,  properly  speaking,  a  re- 
fractive instrument.  It  was  never  intended  to  be  used  for 
detecting  or  measuring  errors  of  refraction,  but  was  de- 
signed for  examining  the  fundus  of  the  eye  for  pathologic 
appearances.  It  can  be  utilized  for  determining,  in  a 
rough  qualitative  fashion,  refractive  errors,  and  instruc- 
tions are  here  given  for  this  purpose.  The  extreme  dif- 
ficulty of  the  technic,  however,  and  the  numerous  sources 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    3? 

of  error,  make  it  a  very  inferior  procedure  to  others  at  the 
refractionist's  disposal. 

Examination  of  the  fundus  with  the  ophthalmoscope 
should  take  place  in  a  darkened  room — not  necessarily 
pitch  dark,  but  sufficiently  darkened  to  induce  relaxation 
and  to  make  the  illuminated  area  of  the  eye  stand  out  in 
contrast  to  the  rest  of  the  room. 

Where  the  ophthalmoscope  is  not  a  self-illuminating 
one,  the  source  of  light — preferably  a  50  C.  P.  incandes- 
cent lamp  enclosed  in  an  opaque  chimney  with  a  diaphragm 
— should  be  placed  to  one  side  of  the  patient  on  the  side 
of  the  eye  to  be  examined,  and  on  a  level  with  the  eye. 
It  must  be  placed  so  that  its  light  may  fall,  without  inter- 
ference, upon  the  mirror  of  the  ophthalmoscope,  when 
this  is  being  held  very  close  to  the  patient's  eye.  As  this 
is  rather  an  awkward  thing  to  do,  a  self-illuminating 
ophthalmoscope  is  greatly  to  be  preferred. 

Direct  Method. 

1.  Patient  and  operator  should  be  seated,  facing  each 
other,  so  that  their  eyes  are  in  the  same  horizontal  plane. 
Operator  must  wear  his  correction,  if  he  needs  any.     Pa- 
tient's accommodation  must  be  thoroughly  relaxed  by  fix- 
ing  at    infinity.      This    relaxation    must   be    maintained 
throughout  the  examination. 

2.  Throw  the  reflected  light  from  the  mirror  into  the 
patient's  pupil ;  then  gradually  approach  nearer  and  nearer 
to  the  patient's  eye,  until  the  mirror  [with  your  eye  at  the 
peep-hole]  is  quite  close  to  his  eye. 


38  TECHNIC   OF   REFRACTION 

3.  Relax  your  own  accommodation.     This  is  the  most 
difficult  part  of  the  procedure  for  the  novice.    It  can  best 
be  done  by  imagining  that  the  fundus  you  are  examining 
is  away  at  the  back  of  the  patient's  head. 

4.  If  the  details  of  the  fundus  do  not  at  once  come  into 
view,  wait  a  few  moments.    Your  accommodation  may  be 
at  fault,  and  may  adjust  itself  in  a  few  seconds.     If  you 
still  do  not  get  a  view  of  the  vessels  and  nerve-head, 
wheel  a  plus  lens  into  the  peep-hole  and  try  again;  if  this 
improves   your   view,    keep   on   wheeling   stronger    and 
stronger  plus  lenses  into  the  peep-hole  until  you  see  the 
fundus.     If  a  plus  lens  makes  things  worse,  try  minus 
lenses. 

5.  The  plus  or  minus  sphere  which  gives  a  clear  view 
of  the  details  of  the  fundus — both  operator's  and  patient's 
accommodation  being  relaxed — is  the  measure  of  the  pa- 
tient's spherical  error. 

6.  If  the  patient  is  astigmatic,  you  will  not  be  able  to 
see  the  details  of  the  fundus  in  all  directions  with  the 
same  spherical  lens  at  the  peep-hole  of  the  mirror.    One 
power  will  give  a  view  of  the  eye-ground  in  one  meridian, 
and  a  different  power  in  the  opposite  meridian.     These 
two  lens-powers  are  the  measures,  respectively,  of  the 
error  in  the  two  meridians. 

7.  To   examine   the    fundus    for   pathological  appear- 
ances, use  the  same  technique  as  given  above ;  in  that  case, 
however,  it  is  not  necessary  to  have  your  accommodation 
relaxed,  or  your  own  error  corrected.     Use  any  accom- 
modation or  lens  that  will  give  a  clear  view  of  the  eye- 
ground. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    39 

Indirect  Method. 

1.  Patient  and  operator  sit  facing  each  other,  about  an 
arm's  length  distant,  with  their  eyes  on  the  same  horizontal 
plane.    Operator  must  wear  his  correction.     Patient's  ac- 
commodation must  be  relaxed  throughout  the  examination. 

2.  With  your  left  hand  hold  a  strong  plus  spherical 
lens,  from  12  D.  to  16  D.,  immediately  in  front  of  the 
patient's  eye  ["objective  lens"]   and  with  the  mirror  at 
your  own  eye,  arm's  length  away,  throw  the  reflected  light, 
through  the  objective  lens,  into  the  patient's  pupil. 

3.  Adjust  the  distance  between  the  objective  lens  and 
the  mirror,  by  moving  the  lens  forward,  or  by  coming  up 
closer  to  it  with  the  mirror,  or  both  manouvres,  until  a 
focussed  image  of  the  patient's  fundus  comes  into  view. 
It  is  a  procedure  which  the  operator  must  work  out  for 
himself,  but  it  is  really  much  easier  technic  than  the  direct 
method. 

4.  Bear  in  mind  that  by  this  method  we  get  a  real,  in- 
verted image  of  the  fundus,  magnified  about  6  times.  By 
this  method,  also,  you   can  view  practically  the  entire 
fundus  at  once,  whereas  by  the  direct  method  you  see 
only  a  part  of  it  at  a  time. 

5.  Now  slowly  withdraw  the  objective  lens  from  the 
patient's  eye,  toward  your  own,  watching  the  image  of  the 
optic  disc.     If  this  image  of  the  disc  remains  the  same 
size,  there  is  no  error  of  refraction. 

6.  If,  on  withdrawing  the  objective  lens,  the  image  of 
the  disc  grows  smaller  the  patient  is  hyperopic,  and  the 
plus  lens  which  makes  it  stay  the  same  size  as  the  meas- 
ure of  the  myopia. 


40  TECHNIC   OF   REFRACTION 

7.  If,  on  withdrawing  the  objective  lens,  the  image  of 
the  disc  grows   larger,  the  patient   is  myopic,   and  the 
minus  sphere  which  makes  it  stay  the  same  size  is  the 
measure  of  the  myopia. 

8.  If  the  image  grows  larger  or  smaller  in  one  merid- 
ian, the  patient  is  astigmatic,  and  the  cylinder,  plus  or 
minus,  which  makes  it  stay  the  same  size  in  all  meridians 
is  the  measure  of  the  astigmatism. 

The  direct  method  is  best  for  detailed  examination 
of  different  areas  of  the  fundus.  The  indirect  method, 
for  a  general  examination  of  the  whole  fundus  and  the 
relations  of  its  various  parts.  For  the  refractionist,  in 
general,  the  indirect  method  is  preferable. 

The  Geneva  Ophthalmoscope  and  Retinoscope. 

To  use  the  instrument  as  an  Ophthalmoscope : 

1.  Turn  on  the  light  and  turn  the  ophthalmoscopic  lens 
into  position.     Rotate  dials  18  and  22  to  zero,  dial  16  to 
OPH. 

2.  Have  patient  place  his  chin  on  the  chin-rest,  and  his 
forehead  against  the  head-rest.     Be  sure  the   face  sets 
squarely  on  the  frame.     Hold  up  your  index  finger  and 
instruct  patient  to  follow  its  movements  while  focussing 
and  examining. 

3.  Looking  past  the  side  of  the  instrument,  adjust  it  so 
that  the  black  dot  which  represents  the  image  of  the  hole 
in  the  mirror  appears  on  the  iris  or  sclera,  and  focus  this 
dot  sharply  by  turning  handles  No.  9  toward  or  from  you, 
as  the  case  may  demand.     [Keep  patient's  eyes  fixed  on 
your  index  finger.] 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS  41 

4.  Having  focussed  the  black  dot,  swing  the  telescope 
of  the  instrument  round  until  the  dot  just  enters  the  pa- 
tient's pupil  on  the  nasal  side.     The  instrument  and  the 
patient's  eye  are  now  in  proper  adjustment  for  viewing 
the  fundus.    However,  slight  readjustments  must  be  made 
by  means  of  moving  the  index  finger  around  [the  patient 
following  its  movements]  until  a  clear  view  is  obtained. 

5.  If  you  yourself  are  presbyopic,  you  must  wear  your 
presbyopic  correction,  either  in  the  form  of  glasses,  or  by 
means  of  the  proper  lens  in  Clip  No.  32  located  just  back 
of  the  eye-cup. 

6.  With  the  black  dot  focussed  as  described,  you  are 
viewing  the  optic  disc  on  the  patient's  fundus.     To  view 
other  portions  of  the  fundus,  move  your  index  finger 
around,  as  desired,  and  have  the  patient  follow  its  move- 
ments.   If,  however,  you  make  any  considerable  range  of 
movement,  it  will  be  necessary  to  swing  the  instrument 
slightly,  so  that  the  patient's  pupil  will  not  go  outside  the 
area  of  light. 

N.  B. — Test  the  focussing  first  with  a  piece  of  white 
paper  in  place  of  the  patient's  face.  If  the  area  of  light, 
when  projected  on  to  this  paper,  is  not  circular,  it  is  be- 
cause the  ophthalmoscopic  lens  is  not  in  a  true  vertical 
position.  To  remedy  this,  first  see  that  the  lens  is  turned 
up  as  far  as  it  will  go,  then  turn  the  small  screw  on  top 
of  tube  just  over  where  the  lens  strikes  when  it  is  up, 
until  the  circle  is  perfectly  round. 


42  TECHNIC   OF   REFRACTION 

CHAPTER  IV. 
THE  OPHTHALMOMETER. 

By  means  of  the  ophthalmometer  we  are  enabled  to 
measure  the  degree  of  curvature  of  the  cornea,  and  thus 
to  determine  whether  it  has  the  same  curvature  in  all 
directions  or  not,  and  if  not,  what  are  the  differences  of 
curvature  in  the  two  chief  meridians.  In  other  words, 
it  enables  us  to  detect  and  to  measure  corneal  astigmatism. 

The  fact  that  there  may  be  lenticular  astigmatism  pres- 
ent, which  is  not  detected  or  measured  by  the  ophthal- 
mometer, does  not  lessen  the  value  of  this  instrument  in 
its  own  field. 

There  are  three  standard  makes  of  ophthalmometer  in 
general  use,  and  instructions  are  here  given  for  using  each 
of  them. 

The  Universal  Ophthalmometer. 

i.  Switch  on  the  lights  before  the  patient  is  seated; 
otherwise  the  noise  of  the  switch,  or  the  sudden  light,  may 
startle  him  and  cause  him  to  move  out  of  position. 

'2.  Focus  the  instrument,  by  turning  the  adjustable  eye- 
piece until  the  cross-hair-lines  are  seen  clearly  and  dis- 
tinctly. They  can  be  made  more  clearly  visible  by  hold- 
ing a  piece  of  white  paper,  before  the  end  of  the  tele- 
scope while  focussing. 

3.  Adjust  the  table  so  that,  with  arms  folded  naturally 
on  the  table  the  patient's  chin  and  forehead  rest  easily  in 
the  frame  provided  for  them.  Instruct  patient  to  lean  his 
forehead  against  the  rest,  and  to  raise  his  eyebrows,  so  as 
to  expose  the  cornea  to  view. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    43 

4.  Raise  or  lower  the  chin  rest,  by  turning  the  knurled 
handle  at  your  end  of  the  telescope,  so  that  patient's  face 
is  upright,  and  the  outer  canthus  of  each  eye  is  in  line 
with  its  respective  white  spot  on  the  head-rest.    This  in- 
sures horizontal  alignment  of  eyes  and  instrument. 

5.  Turn  the  dial  so  that  both  sight  holes  are  horizontal 
and  the  figure  45  on  the  larger  dial  is  at  the  top  of  the 
instrument.     Then  raise  or  lower  the  instrument,  by  means 


of  the  large  knurled  handle  at  your  end,  until  the  white 
spot  at  the  side  of  the  head-rest  is  visible  through  the 
sight-hole.  Swing  the  blinder  attached  to  the  head-rest 
until  it  covers  the  eye  which  is  not  under  examination. 
Then  swing  the  telescope  until  the  eye  to  be  examined 
is  directly  before  the  sighthole.  Instruct  patient  to  look- 
steadily  into  the  telescope. 

6.  Adjust  the  telescope,  by  raising  or  lowering  or  turn- 
ing from  side  to  side,  until  the  images  of  the  mires  are 


44  TECHNIC  OF   REFRACTION 

located,   and   the  central   images   centered  on  the  cross 
hairs.     (Disregard  the  outer  images.) 

7.  Lock  the  telescope  by  pulling  toward  you  the  locking 
handle  on  right  side  of  upright. 

8.  Turn  the  focussing  wheel  on  side  of  telescope  until 
the  images  of  the  mires  are  clear  and  distinct. 

You  are  now  ready  to  begin  to  make  observations. 

9.  Take  hold  of  the  rough  grip  section  of  the  telescope 
and  revolve  it  until  the  black  lines  running  through  the 
middle  of  the  two  mires  are  in  one  straight  line.    This  lo- 
cates the  first  principal  meridian  of  the  eye. 

10.  Turn  one  of  the  pegs  on  the  disc  and  turn  the  disc 
either  way  until  the  inner  edge  of  one  mire  just  makes 
contact  with  the  inner  edge  of  the  other  mire. 

The  white  double  pointer  now  registers  on  the  small 
dial  the  angle  of  the  meridian,  and  on  the  larger  dial  its 
dioptric  value.  Make  notation  of  these  data. 

11.  Revolve  the  telescope,  as  before,  until  the  middle 
lines  of  the  mires  are  again  in  a  straight  line  with  each 
other,  and  again  turn  the  disc,  by  means  of  a  peg,  until 
the  inner  edges  of  the  two  mires  are  just  in  contact. 

The  white  double  pointer  now  registers  on  the  small 
dial  the  angle  of  the  second  principal  meridian,  and  on 
the  larger  dial  its  dioptric  value.  Make  notation  as  be- 
fore. 

You  now  have  the  angles  and  dioptric  values  of  the 
two  principal  meridians  of  the  eye. 

12.  If  the  values  of  the  two  meridians  are  equal,  there 
is  no  corneal  astigmatism.     If  they  are  not  equal,  then 
there  is  an  astigmatism  equal  to  the  difference  between 
the  two  values. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    45 

13.  If  you  correct  by  means  of  minus  cylinder,  the 
power  of  the  cylinder  will  be  the  difference  between  the 
two  meridians,  and  the  axis  in  the  meridian  of  lower  diop- 
tric value.  If  with  plus  cylinder,  the  power  of  the  cylinder 
will  still  be  the  difference  between  the  two  meridians,  but 
the  axis  will  lie  in  the  meridian  of  greater  dioptric  value. 

The  C-I  Ophthalmometer. 

1.  Switch  on  the  lights,  as  instructed  above. 

2.  Focus  the  instrument,  by  means  of  the  knurled  brass 
handle  on  the  left  side,  until  the  images  of  the  mires  are 
clear  and  distinct. 

3.  Adjust  the  table  so  that,  with  arms  folded  on  the 


table,  patient's  chin  rests  comfortably  on  the  chin-rest  and 
his  forehead  against  the  head-rest.  See  that  the  eyes  are 
level,  and  swing  the  cover  over  the  unexamined  eye. 


46  TECHNIC   OF   REFRACTION 

4.  Set  the  perforated  meridian  pointer  to  90  deg.   Sight 
through  the  perforation  in  the  hand,  and  the  disc,  which 
serve  as  sights.     Set  the  instrument  just  below  the  eye, 
then  sight  through  the  telescope,  and  slowly  raise  the  in- 
strument until  the  images  of  the  mires  are  seen  reflected 
from  the  cornea. 

5.  Focus  the  instrument,  by  means  of  the  knurled  brass 
handle  on  the  left  side,  until  the  images  of  the  mire  are 
clear  and  distinct. 

You  are  now  ready  to  make  observations. 

6.  Set  the  eye-piece  at  Primary  position,  and  rotate  the 
large  disc  containing  the  mires  until  the  horizontal  lines 
through  the  middle  of  the  mires  make  one  continuous 
straight  line.    This  locates  the  first  principal  meridian. 

7.  Rotate  the  adjusting  wheel  on  the  right  side  of  the 
telescope  until  the  two  spurs  on  the  horizontal  meridian 
line  between  the  mires  form  a  perfect  cross. 

The  indicators  now  show  the  angle  of  the  first  merid- 
ian, the  radius  of  curvature,  and  the  dioptric  value. 
The  angle,  or  axis,  is  read  from  the  dial  just  back  of 
the  disc,  the  radius  from  the  right  side  of  the  adjusting 
wheel  fixed  to  the  lower  side  of  the  telescope,  and  the 
dioptric  value  from  the  face  of  the  adjusting  wheel. 

8.  Rotate  the  eye-piece  to  Secondary  position,  and  set 
the  left  wheel  to  o,  at  the  same  time  holding  the  right 
wheel  to  form  a  cross.     If  the  cornea  is  spherical,  the 
spurs  will  be  seen  still  to  form  a  gross.    If  there  is  astig- 
matism, they  will  have  separated,  and  must  be  again  made 
to  form  a  cross  by  turning  the  adjusting  wheel  on  the 
right  side  of  the  telescope. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    47 

The  axis,  radius  of  curvature,  and  dioptric  value  of 
the  second  principal  meridian  may  now  be  read  as  be- 
fore. 

9.  The  difference  in  values  of  the  two  meridians  is 
registered  on  the  left  wheel ;  also  whether  the  astigmatism 
is  with  or  against  the  rule. 

10.  If  you  correct  by  means  of  a  minus  cylinder,  the 
axis  must  be  placed  in  the  meridian  of  least  dioptric  value. 
If  with  a  plus  cylinder,  in  the  meridian  of  greatest  diop- 
trism. 

N.  B. — In  astigmatism  against  the  rule,  i.e.,  where  the 
vertical  meridian  is  the  meridian  of  least  refraction,  the 
full  correction  indicated  by  the  instrument  will  usually 
be  acepted  by  the  patient.  But  where  it  is  with  the  rule, 
it  is  usually  necessary  to  deduct  somewhere  in  the  neigh- 
borhood of  .50  D.,  owing  to  the  distance  of  the  correcting 
lens  from  the  eye.  If  the  lens  is  plus,  this  increases  its 
value ;  if  minus,  it  decreases  it. 

The  Meyrowitz-Javal  Ophthalmometer. 

1.  Seat  the  patient  comfortably.     Raise  or  lower  the 
chin  rest  until  the  eyes  are  in  line  with  and  level  with  the 
white  index  marks  on  the  head  rest.     Cover  the  eye  not 
under  examination. 

2.  Place  the  arc  bearing  the  mires  to  the  horizontal 
position,  with  the  axis-indicator  pointing  to  zero. 

3.  Sight  along  the  barrel  of  the  telescope,  and  raise  or 
lower  the  telescope,  also  swing  it  to  left  or  right,  as  may 
be  required,  until  it  points  at  the  eye  to  be  examined. 


48  TECHNIC   OF   REFRACTION 

4.  Turn  on  lights.  Look  through  the  telescope,  and 
continue  the  adjusting  movements  above  described  until 
four  images  of  the  mires  are  seen,  two  being  central  and 
two  on  either  side.  Ignore  the  two  outer  images  and  re- 
gard only  the  two  central  ones.  Focus  the  images  as 
sharply  as  possible. 


5.  Rotate  the  telescope  about  its  long  axis  to  right  or 
left  within  45  degrees  of  the  horizontal,  until  the  central 
black  lines  of  the  two  central  mires  are  in  the  same 
straight  line  [though  not  necessarily,  at  this  time,  a  con- 
tinuous line.] 

6.  Rotate  the  corrugated  stem  projecting  from  the  mire- 
carrying  arc  until  the  edges  of  the  mires  are  just  in  con- 
tact. 

The  axis-indicator  now  registers  the  angle  of  the 
first  chief  meridian.  The  pointer  on  the  parallelogram 
mire  registers  the  dioptric  value  of  this  meridian  on 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    49 

the  scale  engraved  on  the  edge  of  the  arc.    The  pointer 
on  the  step  mire  indicates  the  radius  of  curvature. 

7.  Rotate  the  telescope  90  degrees  to  the  left,  and  again 
rotate  the  corrugated  stem  [if  necessary]  until  the  edges 
of  the  mires  are  just  in  contact. 

The  axis-indicator  now  registers  the  angle  of  the  sec- 
ond chief  meridian ;  the  parallelogram  pointer  shows 
its  dioptric  value ;  and  the  step-mire  pointer  the  radius 
of  curvature. 

8.  If  the  dioptric  values  of  the  two  chief  meridians 
are  equal,  or  if,  on  rotating  the  telescope  to  the  secondary 
position,  the  edges  of  the  mires  are  seen  to  be  still  just 
in  contact,  there  is  no  astigmatism.    If  they  are  not  equal, 
then  there  is  an  astigmatism  equal  to  the  difference  be- 
tween the  two  values. 

9.  If  the  mires,  in  the  secondary  position,  overlap,  the 
astigmatism  is  "with  the  rule,"  and  calls  for  a  plus  cylin- 
der with  its  axis  at  the  angle  shown  by  the  axis-indicator 
"A"  or  a  minus  cylinder  with  its  axis  as  shown  by  the 
plain  pointer.    If  the  mires,  in  the  secondary  position,  are 
separated,  the  astigmatism  is  "against  the  rule,"  calling 
for  a  minus  cylinder  with  its  axis  as  shown  by  the  axis- 
indicator  "A"  or  a  plus  cylinder  with  its  axis  as  shown  by 
the  plain  pointer. 

N.  B. — Only  in  the  two  chief  meridians  of  an  astig- 
matic eye  do  the  central  black  lines  of  the  mires  form  a 
straight  line  with  each  other.  In  every  intermediate  mer- 
idian they  form  a  broken  line. 


50 


CHAPTER  V. 
THE  PHOROPTOMETER. 

As  the  name  implies,  the  original  and  essential  purpose 
of  this  form  of  instrument  is  for  the  detection  and  meas- 
urement of  muscular  imbalance.  However,  as  a  matter 
of  fact,  it  is  a  combination  of  apparatus  for  measuring 
ocular  refraction  and  testing  the  extrinsic  muscles.  It  is, 
in  short,  a  mechanical  assemblage  of  all  the  principles 
and  materials  of  the  trial  case,  in  a  form  and  arrangement 
which  render  it  much  more  convenient  and  accurate  than 
the  case. 

There  are  three  standard  makes  of  this  instrument  in 
the  field,  and  instructions  are  here  given  for  each  of  them. 

The  DeZeng  Phorometer,  Phoroptor  or  Phoro- 
Optometer. 

For  testing  refraction,  proceed  as  follows : 

1.  Align  the  instrument  vertically  and  horizontally  with 
the  distance  chart,  adjust  the  brow-rest  or  eye  cups  and 
pupillary  slides  to  their  respective  positions,  and  the  spirit- 
level  to  horizontal  balance.     Remove  the  phorometer  at- 
tachment  (if  the  instrument  carries  one),  the  Maddox 
rods,  and  the  double  rotary  prisms  from  their  positions, 
the  former  by  folding  forward  and  downward,  the  latter 
by  swinging  to  right  and  left. 

2.  When  using  the  phorometer  trial  frame  instrument, 
place  your  spherical  and  cylindrical  lenses  from  the  trial 
case  before  the  eyes,  in  the  same  manner  as  in  the  use  of 
the  ordinary  trial  case,  the  spherical  lenses  in  the  rear 
cells  and  the  cylinders  in  the  front  revolving  cells. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    51 

3.  When  employing  the  Phoroptor  or  Phoro-Optome- 
ter,  instead  of  using  spherical  lenses  from  the  trial  case, 
wheel  into  place  before  the  eye  the  spherical  lenses  at- 
tached to  the  instrument,  combining  the  lenses  in  the  dif- 
ferent discs  to  make  whatever  power  is  desired. 


If  the  instrument  does  not  carry  a  battery  of  cylinders, 
use  cylindrical  lenses  from  the  trial  case,  placing  them  in 
the  front  revolving  cells,  and  turning  them  to  desired 
axes. 

4.  Proceed  with  these  lenses  in  the  manner  described 
under  TRIAL  CASE. 

Maddox  Rod  Test. 

i.  For  testing  the  horizontal  muscles,  set  the  axis  of  the 
multiple  rods  horizontal  (or  at  180  degrees),  and  direct 


52  TECHNIC    OF   REFRACTION 

the  patient's  attention  to  a  small  circle  of  light  20  feet 
distant. 

2.  If  the  vertical  streak  and  the  circle  of  light  are  sepa- 
rated homonymously,   i.e.,  the  streak  appearing  on  the 
same  side  as  the  eye  wearing  the  Maddox  rod,  the  error 
is  one  of  esophoria. 

3.  Swing  the  rotary  prism  into  position,  with  the  indi- 
cator set  at  zero.     Gradually  rotate  the  indicator  down- 
ward and  outward,  producing  prism-power  base  out,  until 
the  streak  and  the  circle  of  light  come  together.    The  de- 
grees indicated  on  the  scale  show  the  amount  of  esophoria 
present. 

4.  If  the  vertical  streak  and  the  circle  of  light  are  sepa- 
rated heteronymously,  i.e.,  the  streak  appearing  on  the 
opposite  side  to  the  eye  wearing  the  Maddox  rods,  the 
error  is  exophoria. 

5.  Swing  the  left-hand  rotary  prism  into  position,  with 
the  indicator  at  zero,  and  gradually  rotate  the  lever  down- 
ward and  inward,  producing  prism-power  base  in,  until 
streak  and  circle  come  together.     The  indicator  on  the 
scale  now  shows  the  degree  of  exophoria. 

6.  For  testing  the  vertical  muscles,  set  the  axis  of  the 
rods  vertical  (or  at  90  degrees). 

7.  If  the  streak  appears  above  the  circle  of  light,  right 
hyperphoria  is  indicated.     If  below,  left  hyperphoria. 

8.  Raise  the  Stevens  Phorometer  into  place,  with  the 
indicator  on  the  right  prism  set  at  O.     (This  throws  the 
handle  inside).     Rotate  the  prisms  gradually  upward  if 
there   is   right  hyperphoria,   downward  if   there  is   left 
hyperphoria,  until  the  streak  and  the  circle  coincide.    The 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    53 

indicator  will  then  show  the  amount  of  error — right  hy- 
perphoria  if  above,  left  hyperphoria  if  below.  Or  the 
amount  of  the  imbalance  may  be  measured  by  using  the 
rotary  prism. 

9.  To  test  the  oblique  muscles,  set  the  Maddox  rod 
with  its  axis  vertical.     If  the  streak  appears  other  than 
horizontal,  there  is  cyclophoria. 

10.  Rotate  the  rod  until  the  streak  appears  vertical.    The 
indicator  will  then  show  the  degree  of  error.    If  it  stands 
to  the  nasal  side,  it  indicates  that  amount  of  minus  cyclo- 
phoria ;  if  to  the  temporal  side,  plus  cyclophoria. 

As  the  above  tests  are  all  binocular,  they  do  not  dis- 
close which  of  the  single  muscles  in  the  various  pairs 
is  at  fault.  They  should  therefore  be  followed  by 
monocular  tests. 

Monocular  Muscle  Tests. 

1 .  To  test  the  lateral  muscles,  place  a  rotary  prism  with 
zero  horizontal  before  the  right  eye,  and  rotate  upward 
to  8  dioptres.  This  will  dissociate  the  images  and  produce 
vertical  diplopia. 

2.  If  the  lower,  or  false,  image  is  seen  directly  below 
the  upper  one  there  is  no  imbalance. 

3.  If  the  lower  image  appears  to  the  right  of  the  upper 
there  is  right  esophoria. 

4.  Swing  a  rotary  prism  with  zero  vertical  before  the 
left  eye,  and  gradually  rotate  it  outward  until  the  two 
images  are  in  vertical  line  with  each  other.     The  indi- 
cator then  shows  the  amount  of  esophoria. 

5.  If  under  the  previous  conditions  the  lower  image 
appears  to  the  left  of  the  upper,  there  is  right  exophoria. 


54  TECHNIC   OF   REFRACTION 

6.  Swing  the  rotary  prism  with  zero  vertical  before 
the  left  eye,  as  before,  and  gradually  rotate  it  inward 
until  the  two  images  are  in  a  vertical  line.    The  indicator 
then  shows  the  degree  of  exophoria. 

7.  Repeat   the   above   procedure   with   the   displacing 
prism  of  8  dioptres,  base  up,  before  the  left  eye,  to  test 
for  left  esophoria  and  exophoria  respectively. 

8.  To  test  the  vertical  muscles,  place  a  rotary  prism 
with  zero  vertical  before  the  right  eye,  and  rotate  the 
prism  inward  to  12  dioptres.    This  dissociates  the  images, 
producing  lateral  diplopia. 

9.  If  the  two  images  are  in  the  same  horizontal  plane 
there  is  no  imbalance. 

10.  If  the  right-hand  image  lies  below  the  left  one  there 
is  right  hyperphoria. 

11.  Swing  a  rotary  prism  unit  with   zero  horizontal 
before  the  left  eye  and  gradually  rotate  the  prism  upward 
until  the  two  images  lie  in  the  same  horizontal  plane.  The 
indicator  then  shows  the  amount  of  right  hyperphoria. 

12.  If,  under  the  previous  conditions,  the  right-hand 
image  lies  above  the  left  one  there  is  right  hypophoria, 
also  called  right  cataphoria. 

13.  Swing  a  rotary  prism  unit,  with  zero  horizontal, 
before  the  left  eye,  as  before,  and  gradually  rotate  down- 
ward until  the  two  images  lie  in  the  same  horizontal  line. 
Indicator  then  shows  the  amount  of  right  hypophoria. 

14.  Repeat  the  above   procedure   with  the   displacing 
prism  of  12  dioptres,  base  in,  before  the  left  eye,  to  test 
for  left  hyperphoria  and  hypophoria  respectively. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    55 

15.  To  test  the  oblique  muscles,  place  a  double  rotary 
prism  with  zero  horizontal  before  the  right  eye  and  rotate 
upward  to  8  dioptres  to  produce  diplopia. 

16.  Place  a  Maddox  rod  before  both  eyes  with  the 
axes  vertical  or  at  90  degrees. 

17.  If  two  streaks  of  light  are  seen,  one  lying  below  the 
other,  parallel  to  each  other,  there  is  no  cyclophoria. 

1 8.  If  the  upper  streak,  seen  by  the  left  eye,  appears 
horizontal,  and  the  lower  streak,  seen  by  the  right  eye, 
is  oblique,  dipping  toward  the  left,  there  is  right  plus 
cyclophoria. 

19.  If   the  upper  streak  is  horizontal  and  the  lower 
streak  dips  toward  the  right,  there  is  right  minus  cyclo- 
phoria. 

20.  Repeat  the  procedure  with   the   displacing  prism 
before  the  left  eye. 

21.  If  the  two  streaks  are  parallel  there  is  no  cyclo- 
phoria. 

22.  If  the  upper  streak  is  horizontal  and  the  lower  one 
clips  to  the  right,  there  is  left  plus  cyclophoria. 

23.  If  the  upper  streak  is  horizontal  while  the  lower 
one  dips  to  the  left,  there  is  left  minus  cyclophoria. 

24.  In  any  of  the  above  cases,  rotate  the  rod  over  the 
cyclophoric  eye  until  the  lines  are  parallel,  and  the  indi- 
cator then  shows  the  degree  of  cyclophoria  existing. 

Duction  Tests. 

In  performing  these  tests,  begin  by  clearing  the  instru- 
ment of  all  except  the  correcting  lenses  if  these  are  to 
be  used. 


56  TECHNIC   OF   REFRACTION 

1.  To  test  the  internal  recti,  place  a  double  rotary  prism 
with  zero  vertical  before  the  right  eye,  and  slowly  rotate 
the  prism  outward  until  the  circle  of  light  separates  into 
two.    Indicator  shows  the  degree  of  right  adduction. 

2.  Repeat  the  test  with  the  rotary  prisms  before  the 
left  eye.     Indicator  shows  the  amount  of  left  adduction. 

3.  To  test  the  external  recti,  place  rotary  prism  with 
zero  vertical  before  the  right  eye  and  slowly  rotate  inward 
until  the  light  breaks.     Indicator  shows  degree  of  ab- 
duction. 

4.  Repeat  the  procedure  with  the  prism  before  the  left 
eye.    Indicator  shows  the  amount  of  left  abduction. 

5.  To  test  the  superior  rectus,  place  prism  with  zero 
horizontal  before  the  right  eye  and  gradually  rotate  up- 
ward until  the  light  breaks.     Indicator  shows  the  degree 
of  right  superduction. 

6.  Repeat  the  test  with  the  prism  before  the  left  eye. 
Indicator  registers  degree  of  left  superduction. 

7.  Place  prism  with  zero  horizontal  before  the  right  eye 
and  gradually  rotate  prisms   downward  until   the  light 
breaks.    Indicator  registers  degree  of  right  subduction. 

8.  Repeat  the  test  with  the  rotary  prism  before  the  left 
eye,  and  indicator  will  show  amount  of  left  subduction. 

9.  To  test  oblique  muscles,  place  a  Maddox  rod  before 
each  eye,  axis  horizontal,  with  the  indicator  at  zero. 

10.  Gradually  rotate  the  right-eye  rod  downward  (nasal 
side)  until  the  parallelism  of  the  lines  breaks,  forming  a 
cross.     The  indicator  shows  the  amount  of  right  minus 
cycloduction. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    57 

11.  Repeat  the  process,  rotating  the  left-eye  rod  down- 
ward (nasal  side)  until  the  line  breaks.    Indicator  shows 
degree  of  left  minus  cycloduction. 

12.  Rotate  the  right  rod  downward    (temporal  side) 
until  the  line  breaks.    Indicator  shows  the  degree  of  right 
plus  cycloduction. 

13.  Repeat   the   test   with  the   left   eye,   rotating  rod 
downward  (temporal  side)   until  the  line  breaks.     Indi- 
cator shows  the  degree  of  left  plus  cycloduction. 

Muscle  Exercises. 

The  procedure  for  exercising  the  ocular  muscles  is  the 
same  as  in  the  duction  tests. 

The  Ski-Optometer. 

1.  Place  the  instrument  in  position,  assuring  yourself 
of  its  horizontal  status  by  means  of  the  spirit  level. 

2.  Adjust  the  inter-pupillary  distance  by  aligning  each 
eye  individually.     Do  this  by  drawing  an  imaginary  ver- 
tical line  downward  from  the  cp-degree  point  on  the  axis 
scale  through  the  center  of  the  pupil. 

3.  Place  the  opaque  disc  before  the  eye  not  to  be  tested 
by  setting  the  supplementary  disc  handle  at  "shut." 

4.  Set  the  lens  battery  at  "open."    With  the  first  turn 
of  the  spherical  lens  battery  toward  the  nasal  side,  a  plus 
6  D.  sphere  is  placed  in  position.     This  will  "fog"  the 
average  patient. 

5.  Gradually  reduce  the  plus  sphere  by  means  of  suc- 
cessive turns  of  the  battery  toward  the  nasal  side  until  the 


58  TECHNIC   OF  REFRACTION 

astigmatic  wheel  chart  just  becomes  visible.  If  all  spokes 
of  the  wheel  are  equally  visible  and  clear  there  is  no 
astigmatism.  If  one  spoke  stands  out  clearer  than  the 
rest  there  is  astigmatism,  in  which  case  proceed  as  fol- 
lows: 

6.  Set  the  axis  indicator  at  the  same  angle  as  repre- 
sented by  the  line  in  the  astigmatic  chart  seen  most  clearly 
by  patient.  This  insures  every  cylinder  to  be  used  auto- 
matically positioning  itself  at  this  axis. 


7.  Beginning  with  the  weakest  (minus)  cylinder,  swing 
successively  stronger  cylinders  before  the  eye  until  all 
lines  in  the  astigmatic  chart  become  equally  clear.     The 
astigmatism  is  measured  and  corrected  by  this  cylinder. 

8.  Now  continue  to  reduce  the  plus  sphere  power  by 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    59 

successive  turns  toward  the  nasal  side  until  patient  reads 
20/20  on  the  type  chart.  The  total  lens  power,  sphere 
and  cylinder,  now  before  the  eye  is  the  measure  and  cor- 
rection of  the  error. 

9.  If,  in  working  from  the  plus  spherical  scale,  the 
"zero"  mark  is  reached  and  patient  is  still  unable  to  read 
20/20   (i.  e.,  patient  is  myopic),  set  battery  at  "open" 
again  and  gradually  rotate  toward  the  temporal  side,  thus 
gradually  increasing  minus  spherical  power  until  20/20 
is  read. 

10.  If,  when  item  5  is  completed,  there  appears  no 
astigmatism,  items  6  and  7  are  omitted. 

Binocular  Muscle  Tests. 

1.  To  make  tests  of  the  lateral  muscles,  set  the  white 
lines  of  the  red  Maddox  rod  either  at  white  zero  or  at 
i8o-degree  line,  with  the  rods  in  horizontal  position,  and 
the  phorometer  on  the  white  neutral  line,  with  handle 
horizontal. 

2.  If  the  red  streak  of  light  appears  vertical,  running 
through  the  spot  of  light,  there  is  no  imbalance. 

3.  If  the  red  streak  does  not  bisect  the  spot  of  light 
there  is  esophoria  or  exophoria.     Rotate  the  handle,  and 
if  the  streak  and  the  spot  move  closer  together,  keep  on 
rotating  it  in  that  direction  until  the  streak  bisects  the 
spot.  If,  on  rotating  the  handle,  the  streak  and  spot  sep- 
arate further,  reverse  the  rotation  of  the  handle  until  the 
streak  bisects  the  spot.    The  indicator  on  the  phorometer 
will  register  on  the  white  scale  whether  the  error  is 
esophoria  or  exophoria,  and  how  much. 


60  TECHNIC   OF   REFRACTION 

In  testing  the  lateral  muscles,  ignore  the  red  scale  and 
employ  only  the  white  scale. 

4.  To  test  the  vertical  muscles,  set  the  single  white  line 
of  the  Maddox  rod,  or  the  indicator,  on  red  zero  and  the 
pointer  of  the  phorometer  on  the  neutral  line  of  the  red 
scale  with  the  handle  pointing  upward. 

5.  If  the  red  streak  appears  horizontal,  bisecting  the 
spot  of  light,  there  is  no  imbalance. 

6.  If  the  streak  does  not  bisect  the  spot  there  is  hyper- 
phoria  or  hypophoria.    Rotate  the  handle,  as  above,  until 
the  streak  bisects  the  spot.    At  the  point  of  bisection  the 
indicator  will  show  the  degree  of  error. 

In  testing  the  vertical  muscles,  employ  the  red  scale 

alone,  ignoring  the  white  scale. 

N.  B. — The  above  tests,  being  binocular,  give  no  infor- 
mation as  to  which  single  muscle  is  at  fault.  They  should 
therefore  be  followed  by  monocular  duction  tests. 

Monocular  Duction  Tests. 

Remove  the  Maddox  rod  and  the  phorometer  from 
operative  position  during  these  tests,  leaving  the  correct- 
ing lenses  in  place  if  required. 

1.  To  test  adduction  of  the  right  eye,  place  the  rotary 
prism  battery  before  this  eye,  with  the  prism  indicator  at 
zero  on  the  prism  upper  scale.     Place  the  two  cyphers 
(o's)  in  vertical  position  with  the  handle  pointing  hori- 
zontally. 

2.  Slowly  rotate  the  rotary  prism  outward  until  the 
largest  letter  on  the  type,  or  the  Greek  cross,  doubles.  The 
reading  on  the  scale  represents  the  degree  of  adduction. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    61 

3.  To  test  the  adduction  of  the  left  eye,  repeat  the 
process  with  the  rotary  prism  battery  before  the  left  eye. 

4.  To  test  abduction  of  the  right  eye,  set  the  battery 
before  that  eye,  exactly  as  described  in  item  i,  and  slowly 
rotate  the  prisms  inward  until  the  letter  or  the  cross 
doubles.    The  reading  on  the  scale  represents  amount  of 
abduction. 

5.  To  test  left  abduction,  repeat  the  procedure  with  the 
rotary  prism  battery  before  the  left  eye. 

6.  To  test   superduction   of   the   right   eye,   place  the 
rotary  prism  battery  before  the  right  eye  with  the  two 
cyphers  lying  horizontally  and  the  handle  pointing  ver- 
tically. 

7.  Slowly  rotate  the  prisms  downward  until  the  letter 
or  the  Greek  cross  breaks.     The  indicator  shows  the  de- 
gree of  right  superduction. 

8.  To   test   superduction   of   the   left  eye,   repeat  the 
process  with  the  prism  battery  before  the  left  eye. 

9.  To  test  subduction  of  the  right  eye,  place  the  prism 
battery  before  the  right  eye  as  described  in  item  6  and 
slowly  rotate  the  prisms  upward  until  the  letter  or  the 
cross  breaks.     Indicator  shows  the  degree  of  right  sub- 
duction. 

10.  To   test    subduction   of   the   left   eye,    repeat   the 
process  with  the  prism  battery  before  the  left  eye. 

Muscle  Exercises. 

The  procedure  for  exercising  the  ocular  muscles  is  the 
same  as  in  the  duction  tests. 


62  TECHNIC   OF  REFRACTION 

The  Genothalmic  Refractor. 

i.  Adjust  the  horizontal  balance  of  the  instrument  by 
means  of  the  spirit  level  which  is  worked  by  the  thumb 
screw  at  back  of  instrument.  Adjust  the  pupillary  dis- 
tance by  means  of  the  lever  in  front  and  at  top  of  disc. 
Fit  the  eyecups  which  act  as  brow  rests  to  the  patient's 
eyes  (these  cups  are  detachable  and  can  be  sterilized  be- 
tween usages).  Remove  phorometer  attachment,  Mad- 


dox  rods  and  rotary  prisms  from  their  position  by  raising 
them  out  of  range. 

2.  Tilt  instrument  slightly  in  at  bottom  to  eliminate 
reflections  when  using  retinoscope. 

3.  To  place  spherical  lens  powers  before  the  eye,  turn 
the  knurled  knob  which  is  below  and  a  little  to  the  outside 
of  the  apertures.    The  dial  registers  the  strength  of  lens 
before  the  eye.     Temporal  turn  of  the  knurled  knobs 
increases,   nasal  turn  decreases  power  of   lenses.     Plus 
spheres  to  17.75  D.  in  quarters,  minus  spheres  to  18.00  D. 
in  quarters. 

To  secure  minus  powers  turn  auxiliary  lens  to  minus 


p.oo  and  proceed  by  decreasing  with  plus  8.75.  Stronger 
than  minus  9.00,  turn  auxiliary  lens  to  minus  18.00  and 
proceed  in  a  like  manner. 

4.  To  place  cylinders  before  the  eye,  turn  the  knurled 
knob  which  is  at  the  outer  edge  of  the  large  disc.    Minus 
cylinders  to  3.75  D.  in  quarters.     Auxiliary  cell  in  back 
of  instrument  for  powers  over  3.75  D.  or  eighths.     Dial 
registers  the  cylinder  power  in  position. 

To  set  axis  of  the  cylinder  push  down  lever  at  the  outer 
side  of  instrument  and  turn  to  desired  angle.  Automatic 
adjustment  locks  it  in  place  when  released. 

5.  Proceed  with  these  batteries  of  spherical  and  cylin- 
drical lenses  as  you  would  with  lenses  from  the  trial  case. 

Maddox  Rod  Test. 

T.  Lower  one  or  both  of  the  Maddox  rods  into  position 
before  the  aperture  or  apertures. 

2.  To  test  the  lateral  muscles  set  axis  of  rod  at  180 
degrees,  directing  patient's  attention  to  spot  of  light. 

3.  If  streak  passes  directly  through  the  spot  of  light 
there  is  no  vertical  imbalance. 

4.  If  they  are  separated  the  streak  appearing  on  the 
opposite  side  of  eye  wearing  the  Maddox  rod  there  is 
exophoria. 

5.  With   Maddox   rod   at   180  over   right  eye,   lower 
rotary  prism  over  left  eye  into  position  with  indicator  at 
zero  vertical.     If  streak  is  displaced  to  the  left  of  the 
spot  of  light,  rotate  the  indicator  producing  prism  base 
in  until   streak  passes  through  spot  of  light,  indicator 
registering  amount  of  exophoria. 

6.  If  they  are  separated  the  streak  appearing  on  the 


«4  TECHNIC   OF   REFRACTION 

same  side  of  the  eye  wearing  the  Maddox  rod  there  is 
esophoria. 

7.  With   Maddox   rod  at    180   over   right  eye,   lower 
rotary  prism  over  left  eye  into  position  with  indicator  at 
zero  vertical.     If  streak  is  displaced  to  the  right  of  the 
spot   of   light   rotate   the   indicator   outward,   producing 
prism  base  out  until  streak  passes  through  spot  of  light, 
indicator  registering  amount  of  esophoria. 

8.  To  test  vertical  imbalance,  set  axis  of  rod  vertical. 

9.  If  streak  and  spot  are  in  the  same  horizontal  plane 
there  is  no  imbalance. 

10.  If  streak  appears  above  spot  there  is  right  hyper- 
phoria ;  if  below  it,  there  is  left  hyperphoria. 

11.  Lower  the  Stevens  phorometer  into  position,  with 
indicator  on  right  prism  set  at  zero.     Rotate  the  prisms 
gradually  upward  if  there  is  right  hyperphoria,  down- 
ward if  there  is  left  hyperphoria,  until  streak  and  spot 
coincide.    Indicator  will  show  the  amount  of  error — right 
hyperphoria  if  above,  left  hyperphoria  if  below.     Or  the 
error  may  be  measured  by  rotary  prisms. 

12.  To  test  oblique  muscles,  set  both  Maddox  rods  with 
axis  vertical.     If  streaks  appear  other  than  horizontal 
there  is  cyclophoria. 

13.  Rotate  one  or  both  rods  until  the  streaks  appear 
parallel.    Indicator,  or  indicators  added  together,  indicate 
amount  of  cyclophoria.    If  to  the  nasal  side,  minus  cyclo- 
phoria ;  if  to  the  temporal  side,  plus  cyclophoria. 

Monocular  Muscle  Tests. 

i.  To  test  lateral  muscles,  place  a  rotary  prism,  zero 
horizontal,  before  the  right  eye  and  rotate  upward  about 
8  dioptres,  to  produce  diplopia. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    65 

2.  If  the  lower  (false)   image  appears  directly  below 
the  upper  (true)  image,  there  is  no  imbalance. 

3.  If  the  lower  image  appears  to  the  right  of  the  upper 
there  is  right  esophoria. 

4.  Place  a  rotary  prism,  zero  vertical,  before  the  left 
eye  and  slowly  rotate  it  until  both  images  are  in  vertical 
line  with  each  other.  Indicator  shows  amount  of  esophoria. 

5.  If,   under   conditions  of   item    i,   the  lower   image 
appears  to  the  left  of  the  upper,  there  is  right  exophoria. 

6.  Place  a  rotary  prism,  zero  vertical,  before  the  right 
eye  and  slowly  rotate  it  until  the  images  are  in  vertical 
line  with  each  other.     Indicator  shows  amount  of  right 
exophoria. 

7.  Repeat  the  above  procedures  with  the  left  eye  to  test 
for  left  esophoria  and  exophoria,  respectively. 

8.  To  test  the  vertical  muscles,  place  a  rotary  prism, 
zero  vertical,  before  the  right  eye  and  rotate  inward  to 
12  dioptres  to  produce  diplopia. 

9.  If  the  two  images  are  in  horizontal  line  with  each 
other  there  is  no  imbalance. 

10.  If  the  right  image  is  below  the  left  one  there  is 
right  hyperphoria. 

11.  Place  a  rotary  prism,  zero  horizontal,  before  the 
left  eye,  and  rotate  upward  until  the  two  images  come 
into  horizontal    line.      Indicator   shows   degree  of   right 
hyperphoria. 

12.  If  the  right  image  is  above  the  left  there  is  right 
cataphoria. 

13.  Place  a  rotary  prism,  zero  horizontal,  before  the 
left  eye,  and  rotate  downward  until  the  images  come  into 


66  TECHNIC    OF   REFRACTION 

horizontal  line.     Indicator  shows  degree  of   right  cata- 
phoria. 

14.  Repeat  process  with  left  eye. 

15.  To  test  oblique  muscles  place  rotary  prism  indi- 
cator zero  vertical  before  the  right  eye,  rotate  indicator 
to  12  prism  dioptres  to  produce  diplopia. 

16.  Place  both  Maddox  rods  before  the  eyes,  axis  90 
degrees. 

17.  If  the  two  streaks  of  light  appear  other  than  paral- 
lel, there  is  cyclophoria. 

18.  Rotate  one  rod  until  the  streaks  become  parallel. 
Indicator  will   show  amount  of  cyclophoria.     If  to  the 
nasal  side,  it  shows  minus  cyclophoria ;  if  to  the  tem- 
poral side,  plus. 

19.  Repeat  the  procedure  with  the  left  eye. 

The  Tropometer. 

This  is  an  instrument  for  measuring  the  range  of  move- 
ments of  the  ocular  muscles. 

1.  Seat  the  patient  in  a  chair  adjusted  to  such  a  height 
that  his  forehead  may  be  comfortably  maintained  against 
the  brow  piece  of  the  head  rest,  with  the  face  in  an  up- 
right position.     Instruct  him  to  take  the  wooden  bit  be- 
tween the  teeth,  and  more  the  stirrup  carrying  this  bit  in 
or  out  and  up  or  down,  as  necessary  to  secure  the  position 
mentioned  above. 

2.  Hinged  to  the  head-rest  is  an  approximately  semi- 
circular shaped  bar.     Swing  this  over  the  patient's  head 
and  push  the  adjustable  bar  at  the  back  forward  so  that 
its  round,  flat  termination  is  pressed  firmly  against  the 
back  of  the  head,  making  movement  impossible. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    67 

3.  Immediately  in  front  of  the  patient's  face  is  a  small 
fixture  carrying  two  arms,  one  with  a  flat  and  one  with 


a  round  terminal.  These  may  be  moved  in  and  out  and 
up  and  down,  and  the  distance  between  them  may  be 
varied.  Adjust  these  so  that  one  of  them  rests  on  the 
bridge  of  the  nose  and  the  other  of  them  in  the  middle 
nf  the  upper  lip  below  the  nose. 

Measuring  the  Ocular  Movements. 

4.  Turn  the  Telescope  at  right  angles  to  the  patient's 
line  of  vision  and  so  that  the  window  in  the  square  box 
may  be  pointed  as  presented  to  the  patient's  eye. 

5.  Adjust  the  height  of  the  Telescope  by  means  of  the 
hand  wheel  at  the  side  of  the  column.    Focus  the  picture 


68  TECHNIC   OF   REFRACTION 

of  the  eye  seen  through  the  Telescope,  by  means  of  the 
hand  wheel  at  the  side  of  the  Telescope,  and  the  scale  in 
the  eyepiece  by  turning  the  eyepiece  to  the  right  or  left, 
as  may  be  required. 

6.  Immediately  in  front  of  the  eyepiece  and  projecting 
from  the  body  of  the  Telescope  is  a  small  handle.    Adjust 
the   scale  horizontally  or   vertically    by    means  of  this 
projection. 

7.  After  the  patient's  head  is  fixed,  move  the  Telescope 
to  the  right  or  left  until  an  image  of  the  patient's  eye  is 
seen.     Sharply  focus  this  image  and  also  the  scale. 

8.  To  measure  the  vertical  excursion  of  the  eye,  turn 
the  scale  so  that  the  divisions  on  it  are  horizontal.    Raise 
or  lower  the  Telescope  until  one  of  the  scale  divisions 
coincides  with  the  Corneal  Meridian.     Ask  the  patient  to 
look  up.     Note  the  excursion  of  this  point  of  reference. 
Ask  the  patient  to  look  down  and  notice  how  far  along 
the  scale  the  Corneal  Meridian  travels  before  it  stops. 

9.  To  measure  a  lateral  excursion  locate  the  scale  so 
that  the  lines  are  vertical.     Swing  the  Telescope  to  the 
right  or  left  until  one  of  these  lines  is  coincident  with  the 
Corneal  Meridian  and  ask  the  patient  to  look  first  to  the 
right  and  then  to  the  left  and  notice  the  angular  excur- 
sion of  the  eye  on  the  scale  division. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    69 

CHAPTER  VI. 
THE  PERIMETER  OR  CAMPIMETER. 

This  instrument  is  for  the  purpose  of  mapping  out  the 
visual  or  retinal  field.  The  essential  principle  is  the  same 
in  every  make  of  instrument.  While  the  patient  fixes  a 
central  fixation  point,  a  small  test-object  is  moved  either 
from  the  periphery  of  an  arc  toward  this  central  point  or 
from  the  central  point  toward  the  periphery.  The  place 
where  the  test  object,  being  thus  moved,  comes  into  the 
patient's  indirect  vision,  or  passes  out  of  vision,  marks  the 
limit  of  the  retinal  field  in  that  meridian.  The  test  is 
repeated  in  every  meridian,  successively,  thus  giving  a 
contour  of  the  retinal  field. 

The  chief  differences  between  campimeters  is  that, 
whereas  the  older  forms  are  monocular,  the  later  models 
are  binocular  or  stereoscopic. 

Standard  Registering  Perimeter. 

J .  Put  the  chart  in  place  in  the  chart-holder  behind  the 
metal  arc. 

2.  Seat  the  patient  comfortably  before  the  instrument 
so  that  his  chin  rests  easily  on  the  chin  rest.  Instruct  him 


70  TECHNIC   OF   REFRACTION 

to  fix  the  central  fixation  mark  on  the  target.    Blank  the 
left  eye. 

3.  Explore  the  visual  field  by  moving  the  test  object 
(fitted  on  to  the  long  handle)    from  the  center  of  the 
target  out  along  the  metal  arc  toward  the  periphery  until 
the  patient,  who  continues  to  fix  the  center,  can  no  longer 
see  the  object.    When  this  point  is  reached,  indicate  it  on 
the  chart  by  punching  it  through  the  perforation  in  the 
metal  arc. 

4.  Revolve  the  metal  arc  to  each  meridian,  successively, 
and  repeat  the  test  in  each  meridian. 

5.  When    all    meridians    have   been    thus    tested    and 
marked,  take  out  the  chart  and  join  up,  with  a  pencil  or 
pen,  the  punch  marks  in  the  chart.    The  result  will  show 
the  visual  field. 

6.  Repeat  the  process  for  the  left  eye. 

The  Stereo-Campimeter. 

By  means  of  this  instrument  the  field  of  vision  can  be 
outlined  with  the  patient  exercising  binocular  fixation 
which,  for  many  reasons,  is  greatly  superior  to  monocular 
fixation. 

1.  Adjust  the  instrument,  by  means  of  the  elevating 
device  and  the  hinge,  to  suit  the  position  and  comfort  of 
the  patient. 

2.  Place  the  test  charts,  as  they  may  be  used,  sym- 
metrically and  axially  with  respect  to  the  center  of  the 
stereo  lens  system  by  making  the  middle  of  the  chart 
coincide  with  the  zero  mark  on  the  millimeter  scale  on 
the  object  stage. 

3.  Set  the  optical  centers  of  the  stereo  lens  system  80 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    71 

mm.  apart,  so  as  to  coincide  with  the  fixing  centers  of 
the  test  charts. 

4.  Instruct  the  patient  to  fix  the  black  and  red  lines. 
If  the  short  red  line  appears  above  or  below  the  center  of 
the  horizontal  black  line,  there  is  hypophoria.    Correct  it 
by  means  of  the  rotation  stereo  prisms. 

5.  If  the  vertical   red  line  bisects  the  black  scale  at 
figure  8  there  is  no  lateral  imbalance.     If  not,  there  is 
imbalance.    Correct  it  by  means  of  the  additional  prisms, 
inserted  in  the  metal  grooves. 


6.  Now  direct  the  patient's  attention  to  the  octagonal 
form  on  the  chart.     (There  should  appear  but  one  octa- 


72  TECHNIC   OF   REFRACTION 

gon. )  Explore  the  field  of  vision  by  moving  the  various 
test  objects  from  the  center  of  the  octagon  outward  until 
patient  loses  sight  of  them,  doing  this  in  the  various 
meridians  and  noting  on  the  charf  the  point  in  each 
meridian  where  the  object  vanishes.  Join  these  points  on 
the  chart;  to  make  the  contour  of  the  visual  field,  and 
compare  it  with  the  normal  figure. 

7.  To  outline  blind  spot  areas  of  large  angular  extent, 
remove  the  metal  cross  bars  and  place  the  Lloyd  slate 
upon  the  object-stage  by  means  of  the  two  metal  grooves 
in  the  slate  which  fit  the  object-stage.  Be  sure  to  push 
the  slate  snugly  home  so  that  the  slate  may  be  in  correct 
relation  with  the  stereo  lens  system.  Outline  the  areas  as 
described  in  section  6. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    73 

CHAPTER  VII. 

TESTS  FOR  COLOR  BLINDNESS. 

For  very  accurate,  scientific  testing  of  color  sense  a 
spectroscope  is  necessary  to  determine  whether  or  not  the 
spectrum  is  shortened,  to  the  patient's  vision,  at  the  red 
end,  and  also,  by  isolating  the  bands  of  color,  to  discover 
how  the  patient  sees  and  compares  the  single  colors.  Foi 
ordinary  purposes,  however,  one  or  other  of  the  following 
tests  are  employed. 

Holmgren's  Wool  Test. 

This  test  is  carried  out  by  means  of  a  definite  series  of 
colored  skeins  of  worsted.  The  principle  of  the  test  is 
that  red  and  green  blind  persons  see  in  the  spectrum  only 
two  colors,  yellow  and  blue,  with  a  neutral  gray  zone 
between  them.  Green  is  the  first  test  color  because  it 
corresponds  in  tint  to  the  neutral  zone,  thus  making  an 
excellent  confusion  color  with  pale  shades  of  gray,  brown 
and  yellow.  Rose  is  the  second,  being  a  mixture  of  red 
and  blue  in  which,  of  course,  the  color-blind  person  sees 
only  blue.  Red  is  the  third,  which  affords  an  excellent 
confusion  with  dark  shades  of  brown  and  gray. 

Test  i.  Ask  the  patient  to  select  from  the  entire  col- 
lection of  skeins,  placed  in  good  daylight,  all  the  colors 
which  in  general  hue  seem  to  him  like  the  large  green 
skein.  The  completely  color-blind  will  select,  with  or 
without  the  greens,  some  confusion  colors,  such  as  grays, 
fawns,  pinks,  yellows.  The  incompletely  color-blind  will 
match  it  with  greens,  to  which  they  will  add  a  few  light 
shades  of  fawn  or  gray.  This  test  indicates  whether  or 


74  TECHNIC   OF   REFRACTION 

not  the  patient  is  color-blind,  completely  or  incompletely. 
For  further  investigation  employ  another  test. 

Test.  2.  Mix  the  colors  up  again  and  ask  the  patient  to 
match  the  rose  skein.  The  color-blind  will  select  always 
the  light  or  dark  shades  of  blue  and  violet.  The  com- 
pletely color-blind  will  choose  blue  or  violet,  with  or  with- 
out purple.  The  green-blind  will  select  green  or  gray, 
without  purple.  A  patient  proven  color-blind  by  Test  i 
is  only  incompletely  so  if  he  matches  rose  with  deep  pur- 
ples alone. 

Test  3.  Ask  the  patient  to  match  the  red  skein.  The 
red-blind  will  select  red  and  the  shades  darker  than  red; 
the  green-blind,  green  and  brown  shades  lighter  than  red. 
Only  markedly  color-blind  persons  fall  down  on  this  test. 

Jennings'  Self-Recording  Test. 

This  is  a  modification  of  the  Holmgren  test.  It  con- 
sists of  a  square  box,  divided  into  two  compartments,  one 
for  the  green  and  one  for  the  rose  test.  The  standard 
skeins  of  green  and  rose,  respectively,  are  attached  to  the 
inside  of  the  box  lid,  and  in  each  compartment  is  a  color 
board,  made  up  of  the  green  and  green-confusion  colors 
on  one  side,  and  of  rose  and  rose-confusion  colors  on  the 
other  side. 

Proceed  with  the  tests  exactly  as  under  the  Holmgren 
method,  except  that  the  patient,  instead  of  laying  the 
skeins  together,  indicates  his  choice  by  thrusting  a  stylus 
into  the  perforated  hole  in  the  center  of  each  color  on  the 
color  board. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    75 

Beneath  the  color  board  is  a  record  sheet,  divided  into 
squares  corresponding  to  the  color  patches  and  marked 
with  a  G  and  an  R,  respectively,  in  those  squares  which 
match  the  green  and  the  rose,  respectively. 

If  the  patient  be  normal  there  will  be  a  punch-mark  on 
the  record  sheet  in  every  square  marked  G  and  R.  Any 
punch  mark  in  a  blank  space  indicates  a  mistake.  If  the 
mistake  is  on  a  horizontal  line  with  the  letter  G  the  mis- 
take was  made  in  the  green  test ;  if  horizontal  with  R  it 
was  made  in  the  rose  test. 

Williams'  Lantern  Test. 

This  test  has  two  specific  aims :  ( i )  To  test  the  color 
perception  in  the  central  retinal  area,  where  light  from  a 
distant  lantern  focuses,  and  (2)  to  determine  the  ability 
of  the  person  to  recognize  and  name  the  colors  of  signals 
which  have  to  be  used  at  night.  In  the  worsted  test  no 
names  are  used,  but  only  colors ;  in  this  test  it  is  impor- 
tant that  the  candidate  be  able  to  give  to  color  sensations 
the  names  which  normal  persons  give  to  them.  It  is, 
therefore,  particularly  applicable  to  railroad  men. 

The  lantern,  screened  by  shutters,  is  lighted  in  a  dark- 
ened room  and  the  colored  glasses  made  to  face  the  candi- 
date. By  means  of  revolving  shutters  the  colored  lights 
are  revealed  to  him. 

Show  the  colors,  two  or  three  at  a  time,  in  the  sequence 
of  the  standard  record  form  used,  and  require  him  to  call 
out  the  names  of  the  colors. 

Where  he  names  the  color  correctly,  write  O.  K.  against 
it  on  the  record ;  where  he  names  it  wrongly,  write  in  the 
name  that  he  gives. 


76  TECHNIC   OF   REFRACTION 

Reject  the  candidate  for  signal  service: 
If  he  calls  a  red  light  green  or  white; 
If  he  calls  a  green  light  red  or  white; 
If  he  calls  a  white  light  red  or  green. 
N.    B. — Persons    are   sometimes   able   to   differentiate 
colors  by  their  luminosity.     To  obviate  this,  vary  the  in- 
tensity of  the  lights  during  the  test. 

It  is  very  important  that  during  the  Williams'  test  you 
make  no  remark  which  will  indicate  whether  the  candi- 
date's answer  is  right  or  wrong. 

Nagel's  Test. 

This  consists  of  a  set  of  cards,  each  bearing  a  series  of 
little  color  discs  arranged  in  a  ring.  In  some  rings  the 
discs  are  all  of  the  same  color  but  in  different  shades ;  in 
others  there  are  two  or  three  different  colors. 

Ask  the  patient  to  indicate  which  of  the  rings  are  mono- 
chromatic, which  dichromatic  and  which  trichromatic. 
His  answers  will  quickly  disclose  the  existence  and  nature 
of  his  color-blindness. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    77 

CHAPTER  VIII. 

MISCELLANEOUS. 

The  Punctumeter. 

By  means  of  this  instrument,  the  working  principle  of 
which  is  the  substitution  of  the  focal  length  of  a  lens  for 
the  lens  itself,  hyperopia,  myopia,  astigmatism  and  accom- 
modation can  all  be  measured. 

To  measure  hyperopia  or  myopia : 

i.  Place  the  letter  target  before  the  eye  and  set  the 
target  holder  out  to  the  plus  5  D.  mark  on  the  scale.  This 
will  fog  the  ordinary  patient. 


2.  Move  the  target  slowly  in  toward  the  patient's  eye 
until  the  small  letters  can  be  read.    Then  very  slowly  and 
gradually  move  it  outward  again,  ^  D.  at  a  time,  as  long 
as  the  letters  can  be  discerned.     The  furthest  point  at 
which  they  can  be  seen  denotes  the  far  point. 

3.  The  amount  of  hyperopia  or  myopia   can  now  be 
read  from  the  scale  on  the  right  side  of  the  bar,  hyperopia 
being  marked   on  the   further   side  of   the   zero   mark, 
myopia  on  the  near  side. 

4.  In  order  to  arrive  at  latent  hyperopia,  compare  the 


78  TECHNIC   OF   REFRACTION 

amount  of  error  registered  on  the  instrument  with  the 
amount  of  the  patient's  accommodation  and  his  age. 
To  measure  astigmatism : 

1.  Place  the  radiating  line  target  before  the  eye  and 
set  the  target  out  at  the  5  D.  mark  on  the  scale,  to  fog 
the  patient. 

2.  Move  the  target  slowly  in  toward  the  patient's  eye 
until  one  of  the  radiating  lines  comes  into  vision,  and  ask 
the  patient  to  tell  the  number  of  this  line.     The  axis  of 
this    line   indicates   the   meridian    of    least   curvature    in 
patient's  eye.     The  line  at  right  angles  to  this  represents 
the  meridian  of  greatest  curvature. 

3.  Now  place  the  cross-line  target  before  the  eye,  with 
its  cross  lines  coinciding  with  the  two  chief  meridians  just 
determined. 

4.  Move  the  target  outward  as  far  as  possible  so  that 
the  patient  can  still  see  one  set  of  lines.    Then  move  the 
supplementary    slide    forward    and    fix    it    by   set-screw 
against  the  target  slide.    Direct  the  patient  to  look  at  the 
other  set  of  lines  and  move  the  target  holder  in  toward 
the  eye  until  these  lines  are  seen  distinctly.    The  distance 
between  the  two  slides  will  then  indicate  the  astigmatic 
error  and  the  power  of  the  correcting  cylinder. 

To  measure  accommodation: 

1.  Correct  any  existing  astigmatism  and  find  the  far 
point  as  described  in  section  2  under  "To  measure  hyper- 
opia  or  myopia."     Move  up  the  supplementary  slide  and 
fix  it  with  a  set-screw  at  this  point. 

2.  Gradually    move    the    target    slide    inward    toward 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    79 

patient's  eye  to  the  nearest  point  at  which  small  letters  can 
be  read.  This  indicates  the  near  point. 

3.  The  number  of  whole  dioptres  and  fractions  of  a 
dioptre  between  the  two  slides  then  indicates  the  total 
amplitude  of  accommodation. 

To  measure  presbyopia : 

1.  Find  the  nearest  point  at  which  the  target  can  be 
placed  to  the  eye  and  the  patient  still  read  the  smallest 
letters. 

2.  The  marking  on  the  scale  at  the'left  side  of  the  bar. 
at  the  point  where  the  target  holder  stands,  indicates  the 
amount  of  reading  correction  for  33  cm.  or  13  inches. 

3.  If  glasses  are  required  for  a  distance  more  or  less 
than  this,  a  proper  amount  of  plus  correction  must  be 
subtracted  from,  or  added  to,  the  figure  shown  on  the  bar. 

The  Ametropometer. 

i.  Adjust  the  stool  or  chair  so  that  the  patient's  eyes 
will  be  at  the  same  height  as  the  eyepiece  of  the  instru- 


80  TECHNIC    OF    REFRACTION 

ment.  Instruct  patient  to  place  the  eye  that  is  being 
tested  close  to  the  eyepiece,  with  head  erect.  If  his  error 
or  refraction  is  too  great  for  him  to  see  the  rings  on  the 
chart,  place  a  plus  or  minus  sphere  in  the  cell  which  will 
enable  him  to  see  two  rings. 

2.  If  patient  is  emmetropic  he  will  see  two  white  rings 
whose  outer  edges  will  just  touch  at  all  meridians  as  the 
disc  of  the  instrument  is  revolved. 

3.  If  patient  is  hyperopic,  the  edges  of  the  white  rings, 
as  the  disc  is  revolved,  will  be  separated  at  all  meridians. 
The  plus  sphere  which  makes  them  just  touch  at  all 
meridians  is  the  measure  and  correction  of  the  error. 

4.  If  patient  is  myopic,  the  edges  of  the  white  rings, 
upon  revolving  the  disc,  will  overlap  in  all  meridians.  The 
minus  sphere  which  causes  them  to  just  touch  in  all 
meridians  is  the  measure  and  correction  of  the  myopia. 

5.  If  the  edges  of  the  rings  just  touch  at  one  meridian 
and  separate  the  opposite  meridian,  patient  has  simple 
hyperopic  astigmatism.     The  plus  lens,  with  its  axis  as 
indicated  by  the  pointer  D,  which  makes  the  edges  just 
touch  in  all  meridians,  is  the  measure  and  correction  of 
the  error. 

6.  If  the  edges  of  the  rings  just  touch  in  one  meridian 
and  overlap  in  the  opposite  one,  patient  has  simple  myopic 
astigmatism  and  the  cylindrical  minus  lens  which  causes 
them  to  just  touch  in  all  meridians,  is  the  measure  and 
correction  of  the  error. 

7.  If  the  rings  are  separated  in  all  meridians  but  have 
a  meridian  of  greatest  and  least  separation,  patient  has 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    81 

compound  hyperopic  astigmatism.  First  find  a  plus  cylin- 
der, with  its  axis  as  indicated  by  the  pointer  D,  which 
renders  the  separation  equal  in  all  meridians ;  then  a  plus 
sphere  which  causes  the  edges  to  just  touch  in  all  merid- 
ians. This  combination  is  the  patient's  proper  correction. 

8.  If  the  rings  overlap  in  all  meridians  but  have  a 
meridian  of  greatest  and  least  overlapping,  patient  has 
compound  myopic  astigmatism.    First  find  a  minus  cylin- 
der which,  with  its  axis  as  indicated  by  the  pointer  D, 
will  render  the  overlapping  equal  in  all  meridians;  then 
a  minus  sphere  which  causes  the  edges  to  just  touch  in  all 
meridians.     This  combination  is  the  patient's  proper  cor- 
rection. 

9.  If  the  rings  are  separated  in  one  meridian  and  over- 
lap in  the  opposite  meridian,  patient  has  mixed  astigma- 
tism.    First  find  a  cylinder,  plus  or  minus,  which,  with 
its  axis  as  indicated  by  the  pointer,  will  render  the  sep- 
aration or  the  overlapping,  as  the  case  may  be,  equal  in 
all  meridians ;  then  a  sphere  of  opposite  curvature  to  the 
cylinder  which  will  cause  the  edges  to  just  touch  in  all 
meridians.    This  combination  is  the  proper  correction. 

The  Dynamic  Refractor. 

The  technique  of  this  instrument  is  exceedingly  simple, 
as  follows : 

1.  Instruct  the  patient  to  look  through  the  eye-prisms 
and  fix  the  chart.     Two  sets  of  lines,  red  circles  and 
arrows  will  appear,  one  below  the  other. 

2.  If  the  lower  arrow  stands  between  C  and  D,  to  the 
right  on  the  upper  line,  accommodation  and  convergence 


82  TECHNIC    OF   REFRACTION 


are  in  harmony  and  the  refraction  of  the  eye  is  normal. 

3.  If  the  lower  arrow  stands  further  to  the  right  than 
E,  there  is  myopia,  and  the  minus  sphere  which  makes  it 
stand  at  the  normal  position,  i.  e.,  between  C  and  D,  is 
the  correction. 

4.  If  the  lower  arrow  stands  to  the  left  of  the  normal 
position,  i.  e.,  to  the  left  of  C,  there  is  hyperopia,  and  the 
plus  sphere  which  makes  it  take  the  normal  position  be- 
tween C  and  D  is  the  measure  of  the  error. 

5.  If  the  lower  red  circle  is  bisected  by  the  horizontal 
upper  line  there  is  no  imbalance  of  the  vertical  muscles. 

6.  If  the  lower  red  circle  is  above  the  upper  line  there 
is  right  hyperphoria;  if  below  it,  there  is  left  hyper- 
phoria.     The  prism  which,  with  its  base  up  or  down,  as 
the  case  may  be,  causes  the  line  to  bisect  the  circle,  is  the 
measure  of  the  vertical  imbalance. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    88 

Interpupillary  Gauge. 
For  measuring  the  interpupillary  distance: 
i.  With  the  bridge  at  one  end  of  the  tubes  resting  on 
the  bridge  of  the  patient's  nose,  properly  centered,  and 
your  own  eyes  applied  to  the  shaded  eyepiece  at  the  other 
end,  instruct  the  patient  to  fix  the  fixation  mark  with  his 
right  eye.     Read  the  millimeter  marks  on  the  two  scales 
above  and  below  the  center  of  the  patient's  pupil. 


2.  Pull  the  shutter-lid  until  the  right  tube  closes  and 
the  left  one  opens.  Repeat  the  procedure  with  the  patient's 
left  eye,   reading  the  two  scales,   above  and  below,  as 
before. 

3.  The  reading  on  the  upper  scale  in  each  case  gives 
the  pupillary  distance  from  the  center  of  the  bridge  for 
distance  glasses.    The  reading  on  the  lower  scale  for  each 
eye  gives  the  pupillary  distance  from  the  center  of  the 
bridge  for  reading  glasses. 

4.  It  is  advisable  to  make  two  or  three  readings  in  each 
case  and  take  the  average  as  your  finding. 


84  TECHNIC    OF    REFRACTION 

The  Placidoscope. 

1.  Place  the  patient  with  his  back  to  the  light.     Seat 
yourself  at  a  convenient  distance  in  front  of  him  and  hold 
the  disc  before  your  eye  in  the  same  manner  as  a  retino- 
scope,  looking  through  the  peep-hole. 

2.  The  reflected  image  of  the  disc  will  appear  on  the 
patient's  cornea  in  the  form  of  a  concentric  set  of  rings. 


3.  If  the  reflected  rings  appear  circular  there  is  no 
corneal  astigmatism.     If  they  appear  elliptical,  there  is 
astigmatism  with  the  long  axis  of  the  ellipse  correspond- 
ing to  the  meridian  of  least  curvature. 

4.  Use  this  device  to  detect  irregular  astigmatism  and 
conical  cornea. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    85 

CHAPTER  IX. 

THE  COMPLETE  EXAMINATION  AND 
RECORD. 

Every  refractionist,  of  course,  has  his  own  method  and 
order  of  procedure  which  he  works  out  for  himself  from 
his  own  experience  and  which  is  undoubtedly  the  best  for 
him.  It  is  obviously  beside  the  mark  to  be  dogmatic  in 
such  a  matter  or  to  insist  that  this  or  that  course  is  the 
ideal  one.  The  important  things  are  [i]  that  the  refrac- 
tionist should  have  a  definite,  orderly  mode  of  procedure 
to  which  [with  detailed  variations,  as  occasion  may  de- 
mand] he  adheres,  for  nothing  weakens  the  patient's  faith 
in  the  operator  and  the  operator's  confidence  in  himself 
like  aimless  pottering,  and  [2]  that  the  patient  be  given 
a  complete  and  thorough  examination,  by  means  of  every 
method  and  appliance  which  modern  science  has  placed  at 
the  operator's  disposal,  and  an  intelligent  record  made  of 
all  the  findings  in  the  case. 

The  mode  of  procedure  here  set  forth  is  necessarily 
that  which  the  author,  from  his  own  experience,  from  his 
observation  of  others'  experience,  and  from  his  knowledge 
of  the  principles  involved,  has  found  to  be  the  most  prac- 
ticable and  productive  of  the  best  results. 
Vision  and  Visual  Acuity. 

Clearly,  the  first  thing  to  do  is  to  ascertain  what  is  the 
patient's  vision,  without  any  help  or  correction,  with  each 
eye  separately  and  with  both  eyes  together.  This  may  be 
done  either  by  Bonder's  method,  i.  e.,  by  means  of  the 
Snellen  type  chart  at  20  feet,  the  vision  being  recorded  as 
a  vulgar  fraction,  of  which  20  [the  normal]  is  the  num- 
erator, and  the  lowest  line  which  can  be  read  by  the  pa- 


86 


TECHNIC   OF   REFRACTION 


tient  is  the  denominator,  or  by  the  Ives  Visual  Acuity 
Test,  in  which  the  vision  is  recorded  as  it  appears  on  the 
scale. 

Thus,  if  by  Bonder's  method  the  patient  reads  the  40 


line  with  the  right  eye  alone,  the  50  line  with  the  left  eye 
alone  and  the  30  line  with  both  eyes,  the  record  will  be : 

O.  D.  20/40 

O.  S.  20/50 

O.  U.  20/30 
Bear  in  mind  that  the  result  of  this  test  does  not  neces- 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    87 

sarily  give  the  patient's  visual  acuity,  but  only  his  vision, 
expressed  in  the  same  terms  as  we  express  visual  acuity. 
The  vision,  without  glasses,  and  the  actual  visual  acuity 
may  be  the  same  thing  or  they  may  not.  In  most  refrac- 
tive cases  they  are  not,  for  in  most  instances  the  patient's 
actual  visual  acuity  is  normal,  as  will  appear  as  soon  as 
he  is  relieved  of  the  handicap  of  refractive  error.  Actual 
visual  acuity  can  be  determined  only  after  refraction  has 
been  rendered  emmetropic  by  the  best  possible  lens  cor- 
rection. Whatever  defect  in  vision  then  remains  is 
attributable  to  a  true  lowering  of  visual  [retinal]  acuity. 
This  test  should  therefore  be  repeated  when  the  patient's 
refraction  has  been  completed. 

Certain  tentative  conclusions  may  be  reached  from  the 
results  of  the  vision  test  which  suggest  the  lines  the  re- 
fraction tests  should  take.  These  conclusions,  however, 
must  not  be  taken  too  seriously,  as  they  often  mislead. 
Thus,  if  the  patient  reads  20/20  or  better,  it  seems  pretty 
certain  that  any  refractive  error  he  may  prove  to  have 
will  be  of  a  hyperopic  nature;  if,  on  the  contrary,  he 
cannot  read  anything  like  20/20 — say  only  20/50 — it  is 
probable  his  error  is  in  the  domain  of  myopia  or  astig- 
matism. However,  high  hyperopes  often  are  unable  to 
read  more  than  25/50,  owing  to  the  smallness  of  the 
image  made  upon  the  retina.  On  the  whole,  it  is  perhaps 
better  to  pay  no  attention  to  these  tentative  conclusions 
but  proceed  in  regular  form  in  each  case. 

If  the  vision  without  lenses  registers  normal  it  is  highly 
improbable  that  any  physical  disease  of  the  f undus  is 
present  and  the  ophthalmoscopic  examination,  in  such 
cases,  may  well  be  omitted. 


88 


If  the  vision  registers  subnormal,  some  refractionists 
here  advocate  and  practice  the  use  of  the  ophthalmoscope, 
to  determine  at  once  whether  any  or  all  of  this  subnor- 
mality  be  due  to  a  physical  condition  of  the  fundus. 
Personally,  the  author  does  not  favor  its  use  at  this  point, 
but  recommends  that  the  refraction  of  the  eyes  be  pro- 
ceeded with,  and  if,  on  completion  of  refraction,  with  its 
best  possible  correction  on,  the  eye  still  registers  subnor- 
mal acuity,  an  ophthalmoscopic  examination  be  then 
made.  The  reason  for  this  order  of  procedure  is  that  an 
ophthalmoscopic  examination  is  very  trying  to  the  patient 
and  often  renders  any  refractive  examination  impossible 
at  that  sitting. 

For  the  same  reason  the  author,  contrary  to  most 
authorities,  does  not  advocate  making  a  retinoscopic  test 
first,  in  spite  of  the  valuable  fore-knowledge  which  it 
affords  the  refractionist  of  the  metropic  conditions,  un- 
less the  subjective  tests  are  to  be  omitted  altogether  and 
the  operator  intends  to  rely  wholly  upon  objective  findings. 

The  same  holds  good  of  the  ophthalmometer. 

Subjective  Tests. 

When  these  are  to  be  used  at  all — and  in  the  author's 
opinion  both  subjective  and  objective  tests  should  be  em- 
ployed in  every  case — they  should  next  be  proceeded  with. 
Which  of  these  and  how  many  of  them  are  to  be  used  is  a 
matter  for  the  operator's  judgment.  They  are,  in  fact,  the 
logical  extension  and  development  of  the  visual  acuity 
test,  carrying  it  into  more  detail. 

Which  of  the  subjective  tests  or  how  many  of  them 
are  to  be  used  is  a  matter  for  the  operator's  judgment. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    89 

As  between  the  Fogging  Test  and  the  Stenopaic  Slit,  it 
may  said,  in  general,  that  the  former  lends  itself  better 
to  hyperopic  cases  and  the  latter  to  myopic;  but  both  are 
often  valuable  in  either  case.  The  Cobalt  Test  should  be 
used  in  every  instance. 

In  recording  the  subjective  tests,  the  findings  of  the 
isst  should  be  set  down  and  not  merely  the  net  corrective 
results.  Thus,  in  the  Fogging  Test,  the  meridianal  line 
[if  any]  which  stands  out  earliest  and  blackest,  should  be 
recorded,  and  the  power  and  axis  of  the  minus  cylinder 
which  equalizes  the  lines.  In  the  Stenopaic  Test,  the 
meridian  of  best  and  worst  vision  and  the  spherical  cor- 
rection for  each  should  be  set  down.  In  the  Cobalt  Test 
each  separate  appearance  of  the  light  and  its  correction 
should  appear  on  the  record. 

The  Punctumeter,  the  Ametropometer  or  the  Dynamic 
Refractor  may  be  added  or  substituted  for  any  of  the 
above  subjective  tests,  each  finding  being  properly  re- 
corded as  the  test  proceeds. 

Objective  Tests. 

Having  now  ascertained  the  patient's  subjective  condi- 
tions in  their  entirety,  objective  tests  are  in  order. 

Corneal  astigmatism  is  first  determined  and  measured 
by  means  of  the  ophthalmometer  and  faithfully  recorded 
just  as  it  appears,  not  [as  some  are  in  the  habit  of  doing" 
as  the  operator  thinks  he  will  presently  modify  it. 

The  retinoscope  should  then  be  used  by  the  static 
method.  Here  again  the  findings  should  be  recorded  for 
each  meridian  that  is  shadowed  and  not  the  final  cor- 
rective results. 


90  TECHNIC    OF    REFRACTION 

Muscle  Tests. 

These  should  now  be  taken  up  and  performed  with  the 
greatest  system  and  thoroughness,  both  as  to  the  examina- 
tion and  as  to  the  record.  They  may  be  carried  out  either 
with  the  trial  case,  Maddox  rod  and  near  convergence 
chart,  or  by  means  of  the  phoroptometer. 

First  ascertain  the  duction  power  of  each  muscle  and 
pair  of  muscles  without  correcting  lenses. 

Next  investigate  the  state  of  muscle  balance  [or  im- 
balance] and  the  accommodation-convergence  relation, 
both  for  far  and  near  point,  with  static  correction  on. 

Of  all  the  phases  of  examination,  the  muscle  tests  call 
for  the  most  detailed  and  complete  record  of  findings. 
The  practice  embodied  in  certain  record-cards  of  record- 
ing muscle  findings  in  a  single  line  is  a  very  futile  and 
misleading  one.  The  result  of  each  separate  test  for  each 
separate  muscle  and  pairs  of  muscles,  must  be  plainly 
and  diagrammatically  set  down  if  the  record  is  to  be  of 
any  diagnostic  value. 

The  Near  Point. 

No  refractive  examination  is  complete  without  an  in- 
vestigation of  the  accommodation  and  the  near  point, 
which  should  never  be  taken  for  granted,  whatever  the 
age  of  the  patient,  as  insufficiencies  and  anomalies  of  ac- 
commodation are  very  common,  even  in  young  adults  and 
children.  Indeed,  the  term  "presbyopia"  and  the  classifi- 
cation of  patients  as  "presbyopes"  had  best  be  left  out  of 
the  refractionist's  category  altogether  and  every  patient's 
accommodation  and  near  point  investigated  sheerly  on  its 
own  basis. 

All  near  point  tests  should  be  conducted  with  the  patient 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    91 

wearing  his  distance  correction,  previously  ascertained. 

The  first  rough  determination  of  the  near  point  may  be 
made  by  means  of  Jaeger's  test  type  or   some   similar 


TYPE  FOB  TESTING  THE  SIGHT 


|«MIJhXnHftn7tCBn<1K»1|rJw>!Vll  rV*?l5u      tSt'Z 


distance  l«n>««.  there  I*  the  advantage  of  having  the 
reading  portion  placed  at  right  angle,  to  the  line 
Of  vleton  InstMd  of  In  a  tlanting  pO.tlt.on.  a*  in  jlvan 

by  the  ordinary  style  of  bifocal  lenses. 
They  also  remove,  to  a  great  extent. the 
reflections  which  annoy  so  many  per- 


chart  and  translated  into  dioptres  to  indicate,  approxi- 
mately, the  patient's  available  accommodation. 

Subjectively,  this  finding  should  be  confirmed  and  de- 
fined by  means  of  the  cross-cylinders.  Objectively,  by 
dynamic  retinoscopy.  This,  as  stated  in  the  section  on 
that  subject,  is  the  principal  value  of  dynamic  retinoscopy. 

Correction  and  Confirmation. 

With  all  the  data  in  hand  which  has  been  derived  from 
the  foregoing  procedure,  the  refractionist  is  now  in  a 
position  to  exercise  his  judgment  as  to  just  what  lens  cor- 
rection the  patient  shall  wear  and  what,  if  anything,  shall 
be  done  with  the  ocular  muscles.  With  this  phase  of  the 


92  TECHNIC    OF    REFRACTION 

matter,  of  course,  this  little  book  of  technic  has  nothing 
to  do. 

Having  decided  upon  the  correction,  it  should  now  be 
placed  in  front  of  the  patient's  eyes  and  its  accuracy  con- 
firmed by  means  of  the  dynamic  refractor  or  by  re- 
subjecting  the  patient  to  the  visual  acuity^  tests,  both  dis- 
tant and  near,  testing  each  eye  separately  and  both  eyes 
together,  as  was  done  at  the  beginning  of  the  examination, 
and  carefully  recording  the  findings  under  correction. 

The  refractionist  now  has  a  complete  case,  both  as  to 
examination  and  also  as  to  record.  If  vision,  with  cor- 
rection on,  is  20/20  and  comfortable,  he  may  regard  the 
case  as  being  satisfactorily  disposed  of,  at  least  until  the 
patient  has  worn  his  correction  for  several  weeks,  when 
a  review  of  the  case  may  be  made. 

The  Ophthalmoscope. 

If,  after  the  refraction  has  been  worked  out  as  thor- 
oughly as  possible  and  the  best  available  correction  been 
given,  the  patient  is  still  unable  to  read  20/20  or  shows 
other  signs  of  poor  vision,  the  visual  acuity  should  again 
be  carefully  ascertained  and  recorded  and  an  examina- 
tion made  of  the  fundus  for  physical  trouble.  Carefully 
record  all  findings. 

The  Visual  Field. 

Whatever  the  ophthalmoscope  may  reveal,  or  even  if  it 
reveals  nothing  at  all,  the  operator  should  proceed  to  ex- 
plore the  visual  field  by  means  of  the  Perimeter  or 
Campimeter,  according  to  directions  given  above.  The 
campimeter  chart,  when  completed,  should  be  attached  to 
and  form  a  part  of  the  record. 


TRIAL  CASE  AND  REFRACTIVE  INSTRUMENTS    93 

With  the  findings  of  the  ophthalmoscope  and  the 
campimeter  before  him,  the  refractionist  is  in  a  fair  posi- 
tion to  continue  to  investigate  any  disease  of  the  eye 
which  may  be  present. 

It  should  be  repeated  here  that  the  order  of  procedure 
above  set  forth  is  subject  to  variation  according  to  the 
preference  or  experience  of  the  individual  operator.  Many 
competent  refractionists,  for  example,  think  it  best  to 
proceed  at  once  to  retinoscopy,  after  taking  the  vision, 
before  employing  the  subjective  tests.  No  doubt,  in 
many  cases  this  method  shortens  the  time  consumed  in 
the  entire  examination  and  also  has  the  advantage  of  fur- 
nishing certain  guiding  information.  As  stated,  the 
author  believes  that  these  advantages  are  more  than  out- 
weighed by  the  tiring  of  the  retina  and  by  the  complete 
picture  of  the  case,  from  the  patient's  standpoint,  which 
is  obtained  by  the  subjective  tests — just  as  in  a  medical 
case  one  always  gains  a  more  intelligent  conception  by 
exploring  thoroughly  all  the  subjective  symptoms  before 
proceeding  to  objective  modes  of  diagnosis.  In  the  last 
analysis,  however,  it  is  a  matter  for  the  individual  oper- 
ators to  determine  for  himself. 


Curren 


BOOKS 

Oculo -Refractive  Cyclopedia  and 
Dictionary — 

By  Thomas  G.  Atkinson,  M.  D.  Complete,  concise,  sim- 
ple, profusely  illustrated.  Price,  $5.00. 

Optical  Shop  Practice — 

By  W.  W.  Merritt.  Thorough  treatise  on  making  of 
lenses,  fully  illustrated.  Price,  $2.00. 

Business  Side  of  Optics — 

By  Roe  Fulkerson.  Invaluable  to  the  practitioner  de- 
siring to  build  up  his  clientele.  Price,  $1.00. 

Transpositions  and  Tables — 

By  Edward  J.  Lueck.  Everything  tabulated  already  for 
you.  Price,  $1.50. 

Text  Boof^  of  Iridiagnosis — 

By  J.  Haskell  Kritzer,  M.  D.  Dealing  with  pathological 
and  functional  disorders  of  the  human  body  indicated  by 
abnormal  lines,  spots  and  discolorations — the  book  you 
have  wanted.  Price,  $5.00.  Also  Wall  Chart  of  Iridiag- 
nosis (32  colored  plates  of  the  iris  and  enlarged  "Iris", 
all  in  colors).  Price,  $2.50.  Text  Book  and  Chart,  $7.00. 

The  Profession; 

17  No.  Wabash  Ave. 


literature 


BOOKS 

Muscles  of  the  Eye — 

By  Geo.  A.  Rogers.  Handling  in  a  simple,  comprehensive, 
masterful  manner,  ocular  muscle  functions  and  their 
anomalies — that  difficult  question  for  practitioner  as  well 
as  student.  Fully  illustrated.  Price,  $3.00. 

FOLDERS 

Interesting  Facts  Concerning  Your  Eyes — 

One  of  the  most  popular  folders  ever  used  by  the 
refractionists.  An  excellent  business-puller.  Per  thou- 
sand, with  your  imprint,  $7.50. 

New  Wrinkles — 

Another  fine  folder  widely  used.  Shows  that  wrinkles 
frequently  indicate  need  for  glasses  or  else  (for  those 
already  wearing  glasses)  different  lenses.  Per  thousand, 
with  your  imprint,  $6.00. 

CARDS 

Meissner  Record  Cards — 

Standardize  and  systematize  your  practice.  Used  all  over 
the  United  States.  Per  thousand,  $4.00. 

Order  from  your  jobber  or 

ress,  Inc. 

CHICAGO 


Oculo- 
Refractive 

Cyclopedia 

and 

Dictionary 

By  THOMAS  G.  ATKINSON,  M.  D.,  B.  Sc. 


A  practical  and  comprehensive  cyclopedia 
of  ocular  refraction  and  all  the  phases  of  op- 
tics, anatomy  and  physiology  of  the  eye  which 
relate  thereto. 

Concise,  clear,  easy  to  consult.  Plain  in 
language,  rich  in  illustration,  graphic  in  pre- 
senting its  subjects. 

Over  400  pages.  Handsomely  and  Substan- 
tially Bound. 

Price  $5.00  Net 

THE  PROFESSIONAL  PRESS,  INC. 

17  N.  Wabash  Avenue  CHICAGO,  ILL. 


JUL 


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THE  LIBRARY 

UNIVERSITY  OF  CALIFORNIA 
LOS  ANGELES 


A     000  387  060     7 


